Scientific article #1

I need it after 24 hours

Scientific Article Discussions

It is important for scientists to be able to read, analyze, and synthesize scientific journal articles in order to answer questions and determine the current state of knowledge on a topic. We will have seven paper discussions over the course of the semester, six led by pairs of students. Each student is required to co-lead one discussion.

The discussion leaders are required to:

1.

Examine the list of questions provided below for their assigned article discussion (#2-7) and choose a question (or come up with your own) that you would like to address with the literature discussion.

2. Find one scientific article that you think addresses that topic. (You will probably need to search through several papers to find one that actually address the question or are interesting to you).

3. Meet with me at least two weeks before the discussion day to look over your topic and journal article. Be sure you read the article before you meet with me! You need to send me the articles you propose to use at least two days in advance of our meeting.

4. On the day of discussion, give a 5-10 minute mini-lesson reiterating what the foundational question was addressed by the paper and then providing background context for the paper and summarizing the key question(s), methods, results, and conclusions. This should incorporate a PowerPoint presentation with the most pertinent (not necessarily all) information and figures…just hit the most relevant items. Try not to provide critique or opinions about the paper during the summary.

5. Facilitate discussion about the paper. Here are some tips (in no particular order) of things you might want to include in your discussion:

a. Try not to let your opinion of the paper dominate the discussion. Encourage everyone to contribute his or her thoughts.

b. Solicit people’s opinions of what they found to be the strongest or weakest parts of the paper. You can ask for everyone to respond, or specific individuals (but spread the love a little).

c. Ask for people to share what confusions they had, or what they thought was unclear.

d. Discuss whether the authors achieved what they set out to do and whether their conclusions were meaningful, reasonably “within the bounds of their data”, and/or important or generalizable to other topics.

e. You can ask people what they would have done differently for this study, or helpful follow-up studies that could be pursued.

f. Ask the group what research questions arose in their minds while reading the article(s).

g. Try to conclude with a brief summary of what ideas/conclusions were produced/shared during the article discussion you just led.

The rest of the class is required to:

1. Read the paper.

2. Write a summary of the key points of each paper and how they relate to larger question being addressed or the course content. This summary must include at least one idea or question for discussion (see the list of discussion tips above and consider making notes about those while reading). The summary should be short (approximately ½-page single-spaced), typed, and brought to the discussion.

3. Participate in the discussion during class. Active participation is essential for discussion and relies on having read the papers. (Your written summary and active participation in discussions accounts for 7.5% of your course grade.)

Article Discussion Possible Questions
: Other questions are possible, so if you have a question that is somewhat related to what we have discussed in class, then suggest that.

Article Discussion #1: (Instructor-led)

How should scientists approach the study of the natural world?

Article Discussion #2:

What environmental traits determine the geographic range of a species?

How to species respond to climate change?

Are native or invasive species better able to adapt to environmental change?

How do animals (or plants) live in the desert with such little water?

Why can some fish live in freshwater, some in salt water, and some can live in either?

How do plants maintain homeostasis of energy production under various environmental conditions?

How do organisms optimize their time when obtaining energy?

Article Discussion #3:

What are the costs and benefits of direct versus indirect development?

What environmental conditions cause variation in modes of reproduction? (between species or within one species)

Why do some organisms produce few offspring while other produce many?

What factors determine when an organism begins to reproduce?

What is better for a larvae to do, develop fast an metamorphose when small or develop more slowly and metamorphose when large?

How do different dispersal methods affect population connectivity?

What factors influence the magnitude of population dispersal?

Are (or when are) some methods of measuring abundance better/worse than others?

How does [insert some aspect of population demographics] influence change in population growth?

What ecological circumstances lead to different types of survival curves (or reproductive timing) in a species (or different species)?

What exerts more influence on populations of [insert species], density-dependent or density independent processes?

How to population outbreaks affect an ecosystem (or community)?

Can population cycles be predicted? How? (Or what factors determine population cycles?)

How impact does the allee have on a population?

More to come for the later discussions…

BIO317 Spring 2018

Thinking of Biology

608 BioScience • July/August 2007 / Vol. 57 No. 7 www.biosciencemag.org

For more than two decades, there has been sustainedcriticism of the appropriateness of using methods that rely
solely on null-hypothesis testing for observational studies in
science (e.g., Carver 1978, McBride et al. 1993, Anderson et
al. 2000, Wade 2000, Johnson 2002). The disciplines of psy-
chology, wildlife biology, and statistics have been in the fore-
front of this conflict between two qualitatively different
inferential paradigms: model-selection methods, based on in-
formation theory, and null-hypothesis testing, based on a
frequentist approach. But many other areas of biology and
ecology have been implicated, including molecular biology,
systematics, physical geography, medicine, and epidemiology
(Johnson and Omland 2004). Perhaps this is because all these
fields readily provide case studies in which multiple causative
factors lead to real-world complexity that is difficult to reduce
to a single, isolated mechanism.

Strong proponents of the model-selection paradigm have
decried the use of null-hypothesis testing as outdated, and
some have colorfully suggested that the practice of reporting
P values should be “euthanized” on philosophical grounds
(Anderson and Burnham 2002). Others have taken an equiv-
ocal stance, suggesting that the two inferential paradigms
provide complementary tools for the investigator, and that hy-
pothesis testing should be retained for manipulative experi-
mental design (e.g., Johnson and Omland 2004). Stephens and
colleagues (2005) proposed that it may be more profitable to
distinguish between studies of univariate causality, in which
null-hypothesis testing may be sufficient, and multivariate
causality, in which model selection offers clear advantages (but
see Lukacs et al. 2007).

Here we attempt to clarify some of the philosophical ter-
rain relevant to this debate by discussing one of the key
philosophical underpinnings of model selection. This is the
concept of the method of multiple working hypotheses
(MMWH), as described by the geologist T. C. Chamberlin in
1890, and later referred to by Platt (1964) in his notion of
“strong inference.” Although the term has become almost
mainstream in ecology, we contend that the core meaning of
Chamberlin’s conceptualization has often been forgotten or
misinterpreted over time, and that this needs rectification. For
instance, a common mistake is to equate the MMWH with
the method of developing alternative hypotheses. Yet sys-
tematic application of the latter method occurred at least as
early as Francis Bacon (1620), whereas the former is qualita-
tively different in construction and was intended by Cham-
berlin to serve as a complement to the formal, “pure,” or
classic analytic method. Here we first describe the MMWH
in general terms. Then we discuss its applicability to method-
ologies that not only allow (or require) the simultaneous
appraisal of more than one hypothesis but explicitly accom-
modate various situations in which several hypotheses are
simultaneously true.

Louis P. Elliott (e-mail: louis.elliott@nt.gov.au) was at the School for

Environmental Research at Charles Darwin University in Australia when

this essay was prepared; he is now with the Northern Territory Department

of Natural Resources, Environment, and the Arts in Australia. Barry W. Brook

(e-mail: barry.brook@adelaide.edu.au) is the director of the Research Institute

for Climate Change and Sustainability, School of Earth and Environmental

Sciences, University of Adelaide, South Australia 5005, Australia. © 2007

American Institute of Biological Sciences.

Revisiting Chamberlin: Multiple
Working Hypotheses for the
21st Century

LOUIS P. ELLIOTT AND BARRY W. BROOK

The method of multiple working hypotheses, developed by the 19th-century geologist T. C. Chamberlin, is an important philosophical contribution
to the domain of hypothesis construction in science. Indeed, the concept is particularly pertinent to recent debate over the relative merits of two
different statistical paradigms: null hypothesis testing and model selection. The theoretical foundations of model selection are often poorly understood
by practitioners of null hypothesis testing, and even many proponents of Chamberlin’s method may not fully appreciate its historical basis.
We contend that the core of Chamberlin’s message, communicated over a century ago, has often been forgotten or misrepresented. Therefore, we
revisit his ideas in light of modern developments. The original source has great value to contemporary ecology and many related disciplines, communicating
thoughtful consideration of both complexity and causality and providing hard-earned wisdom applicable to this new age of uncertainty.

Keywords: Bayesian statistics, hypothesis testing, model selection, philosophy of science, statistical significance

www.biosciencemag.org July/August 2007 / Vol. 57 No. 7 • BioScience 609

The method of multiple working hypotheses
The concept of the MMWH was advocated over a century ago
by the geologist Thomas Chamberlin (1890) in a paper that
was later reprinted in Science—a testament to the perceived
importance of its content. “With this method,” Chamberlin
wrote, “the dangers of parental affection for a favorite theory
can be circumvented” (Chamberlin 1890). Chamberlin’s con-
cerns have a timeless quality that makes his prose lucid and
relevant even today. He contrasted the MMWH with the
methods of the “ruling hypothesis” and the “single working
hypothesis,” and contended that the ruling hypothesis is the
worse of the latter two. This is because investigators’ affection
or loyalty to a theory may lead them to collect evidence to
support only the ruling theory, and not sufficiently consider
alternative explanations. Chamberlin also criticized the
single-working-hypothesis approach, said to be the method
of the day: “Under the working hypothesis, the facts are
sought for the purpose of ultimate induction and demon-
stration, the hypothesis being but a means for the more
ready…arrangement and preservation of material for the
final induction” (Chamberlin 1890).

The amendment that Chamberlin advocated is one
familiar to all practitioners of science. However, like much
cogent advice, it is easier to follow in theory than in prac-
tice: “[What is required] is to bring up into view every ra-
tional explanation of new phenomena, and to develop every
tenable hypothesis respecting their cause and history”
(Chamberlin 1890). This description approaches the true
purpose of the MMWH: to circumvent the dangers of be-
coming emotionally attached to any given idea or hypoth-
esis, and to work against the natural tendency to construct
premature (or to require single and complete) explanations
of phenomena. The approach is a carefully considered one,
which poses such questions as “Is this really the full expla-
nation?” or “Are we seeking to prematurely establish the
truth of a single factor, when consideration of more than one
may be more appropriate?”

Explicitly describing “synthetic cognition.” Chamberlin
claimed that after a period of time of following the applica-
tion of the MMWH, a habit of thought develops that is anal-
ogous to the method itself:

Phenomena appear to become capable of being viewed
analytically and synthetically at once. It is not altogether
unlike the study of a landscape, from which there comes
into the mind myriads of lines of intelligence, which are
received and coordinated simultaneously, producing a
complex impression which is recorded and studied
directly in its complexity. My description of this process
is confessedly inadequate…but I address myself to natu-
ralists who I think can respond to its verity from their
own experience. (Chamberlin 1890)

This is a description of the processes by which researchers
both tolerate and benefit from intellectual dissonance when

confronted by complexity. Confounding variables and mech-
anisms can operate at different temporal and spatial scales,
both in succession and simultaneously. This is often the case
in diachronic problems in ecology, conservation biology,
paleontology, epidemiology, medicine, geology, meteorol-
ogy, and astronomy (Hilborn and Mangel 1997), in which it
is often impossible to “wind back the clock” or to experiment
on the systems involved; mechanisms must be inferred from
other lines of evidence and later brought together into a con-
sistent whole.

Chamberlin particularly stressed the importance of not be-
ing content with the idea of a single, often simple explanation,
despite the pleasure that such an explanation may arouse in
the mind of the researcher. Being a geologist, he used as a
prime example the question of the origin of the Great Lakes
basins. There are at least three “practically demonstrable”
mechanisms by which the basins could have formed: (1)
crust deformation, (2) preglacial erosion from rivers, and
(3) glacial excavation (Chamberlin 1890). Whereas another
researcher might have been content with one, or perhaps
two, of these hypotheses, Chamberlin invoked all three of
them, proposing that all three processes acted in temporal
succession to produce the end result. This is commonly de-
scribed as a “cascade” in ecology, and in medicine it corre-
sponds to the distinction made between a primary and a
secondary condition. For example, although a person may have
died from heart disease, this illness would most likely have had
prior contributing factors such as poor diet, lack of exercise,
and smoking.

Sequential and simultaneous multiple working hypotheses.
Although Chamberlin did not make any formal distinction,
it is useful to consider whether there may be different types
of multiple working hypotheses. Causation, for instance,
may occur as a series of sequential steps (figure 1a; e.g., a
disease-ridden animal may be vulnerable to predation),
or multiple factors (of varying importance) may operate
simultaneously (figure 1b). Multiple working hypotheses in
series (figure 1a) may, from the perspective of the observer,
appear simultaneously true, yet may be separated in time by
a sequence of state changes, with later actions and effects
being dependent on former ones. In contrast, multiple work-
ing hypotheses in parallel (figure 1b) may, in practice, indeed
be simultaneously true, and operate either independently or
in interaction. This difference is important when considering
how researchers might evaluate such hypotheses statistically,
because multiple working hypotheses in series may be more
readily distinguishable from each other as a result of their sep-
aration in time, and may thus be more easily approached by
methods that test hypotheses one at a time. And although con-
temporary methods that explicitly accommodate the simul-
taneous comparison of hypotheses (e.g., model selection)
may be applicable to both types of causation, they may be
particularly well suited to scenarios in which multiple factors
operate in parallel (figure 1b).

Thinking of Biology

Thinking of Biology

610 BioScience • July/August 2007 / Vol. 57 No. 7 www.biosciencemag.org

As a real-world ecological example of multiple factors
working in parallel, Allan C. Fisher Jr. (1980) described a
scene of rapid ecological change in Chesapeake Bay, the
largest estuary system on the eastern coast of the United
States. The bay serves as a hydrological mixing bowl, receiv-
ing fresh water from a number of tributaries and tidal salt
water from the sea. Between 1968 and 1980, oyster sets in the
lower James River were observed to decline from 2000 to
200 oysters per bushel, at a time when the rate of effluent in
the tributaries had increased substantially. This effluent con-
sisted of raw and chlorinated sewage, pesticides, herbicides and
fertilizers from agriculture, heavy metals from industrial
waste, and large volumes of sediment caused by erosion—
excessive particulate matter that deprives oysters of oxygen
for part of the year. Overly fresh water can also affect oysters,
because they can only briefly tolerate saline solutions of less
than five parts per thousand. In 1972, Hurricane Agnes wiped
out over two million bushels and eliminated oysters entirely
from some parts of the bay. There was also a devastating
oyster disease, MSX (multinucleated sphere X [unknown]),
which arrived in 1959 and, as the name implies, about which
very little was known.

To answer the broad question of what caused the reduced
rate of oyster set in the lower James River, there are a num-
ber of potentially interrelated factors to which we might at-
tribute blame. It turns out that MSX is caused by a
spore-forming protozoan (Haplosporidium nelsoni), which was
found not to affect oyster larvae strongly because it cannot tol-
erate the relatively low salinity of the lower James. Further,
it is possible to discount the hypothesis that Hurricane Agnes
was responsible for the overall decline, because the oyster pop-
ulations in the affected areas recovered after this event. But
the other factors appear difficult to separate. Fisher (1980)
concluded that “a combination of factors is putting the
oyster larvae in great stress.” And although only one factor (e.g.,
chlorine levels) may have actually been responsible, it is quite
possible that several factors (“working hypotheses”) acted
simultaneously.

Chamberlin’s method and Bradford-Hill’s guidelines for
causation. It is extremely difficult to prove causation in ob-
servational (and many experimental) studies, in part be-
cause there are usually many factors researchers cannot
adequately control. As such, Austin Bradford-Hill (1966) in-
stead developed a set of guidelines (later called “criteria” by
others) for establishing causation in medicine and other
fields (Phillips and Goodman 2004). These guidelines were
used and accepted by the US Supreme Court in the case of
Daubert v. Merrill Dow Pharmaceuticals (509 U.S. 579 [1993]),
establishing legal precedence. On the basis of this decision,
judges could deny the efficacy of defenses such as “There is
no statistical evidence to prove that smoking causes lung
cancer,” which fail to acknowledge that investigators can use
auxiliary information to infer whether causation is likely or
to determine what is biologically plausible. Bradford-Hill
did, however, overestimate people’s ability to assess numer-

ical and probabilistic relationships; later work in the 1970s and
1980s demonstrated that laypeople have poor quantitative
intuition (Phillips and Goodman 2004).

Chamberlin’s description of the MMWH is concordant
with Bradford-Hill’s guidelines. “The effort,” Chamberlin
wrote, “is to bring up into view every rational explanation of
new phenomena and to develop every tenable hypothesis
respecting their cause and history” (Chamberlin 1890).
Bradford-Hill (1966) suggested that a rational approach to
establishing causation would include concepts such as “con-
sistency, temporal sequence, coherence with biological back-
ground and previous knowledge, [and] biological plausibility.”
In this sense, Bradford-Hill and Chamberlin both describe a
general method of inference as it applies to causation. Their
concerns are specifically pertinent to step 3 in figure 2a (“In-
fer that the difference is caused by the treatment and is not
due to chance or placebo”) and steps 3 and 4 in figure 2b
(“Consider what correlations exist between biologically sig-
nificant variables…and how they interact in a complex system”
and “Infer from all available data what might have caused the
differences observed”). In a system in which a researcher can
adequately control for extraneous factors and manipulate
the factor under consideration, the pathway described in
figure 2a, simple experimental design, is likely to be the more
direct inferential route. Of course, many studies do not
permit this luxury, and in these cases the process of inference
must necessarily rely to a much greater extent on other kinds
of knowledge (observational study; figure 2b).

“Strong inference” and the method
of multiple working hypotheses
In the article “Strong Inference,” John Platt (1964) clearly de-
scribed the classic analytic method of science, first attributed
to Bacon (1620). It requires a three-step process: (1) devel-
oping alternative hypotheses, (2) devising a set of crucial
experiments to eliminate all but one of the hypotheses, and
(3) performing the experiments. In its ideal representation,

Figure 1. Comparison of two possible types of natural sys-
tem where the method of multiple working hypotheses is
applicable. Multiple factors can lead to a state transition
both (a) in series (e.g., chains of extinction), where two or
more factors occur sequentially, and (b) in parallel (e.g.,
ecosystem degradation), where the relative strength of
simultaneous factors is indicated by the line thickness.

the method is unidirectional, because progress is built on what
has been tested, through the systematic growth and pruning
of branches on a tree of scientific knowledge.

Platt (1964) argued, however, that the doctrine of dis-
proof and falsifiability tends to force scientists to be either
“soft-headed or disputatious.” His implication was that there
is a deficiency in the way scientists conduct their affairs when
they proceed by negatives, a process that can lead to combative
thought. Platt suggested that to be overly contentious in sci-
ence can be counterproductive, because it makes some peo-
ple shy away from using the benefits of the classic analytic
method. Others are left vulnerable to the workings of the ego
and to the risks of becoming emotionally attached to their rul-
ing hypotheses, an outcome with its own inherent dangers to
the spirit. Platt’s solution was the application of Chamberlin’s
MMWH, and he called for the reprinting of Chamberlin’s
1890 paper “where it could be required reading for every
graduate student—and for every professor” (Platt 1964).
However, although there are aspects of Chamberlin’s method
that are compatible with the classic analytic method as ex-
pressed by Platt (1964), there are also important differences
that were not fully appreciated at the time.

Differences between Chamberlin’s method and the classic
analytic method. The key difference is that Chamberlin’s
MMWH recognizes explicitly the possibility that more than
one hypothesis may be simultaneously true, while the clas-
sic analytic method, as espoused by Platt (1964), recognizes
only that there is uncertainty as to which hypothesis repre-

sents truth. This does not imply that the use
of the MMWH necessitates the introduction
of complexity where a simple explanation
will suffice. Rather, if more than one cause
can be shown to exist, then the question
becomes, What is their relative importance,
and how do they interact? Further, under the
MMWH these hypotheses are not framed as
alternatives to be falsified in order to pro-
vide material for Bacon’s method of infer-
ence. Indeed, Chamberlin’s MMWH does
not anticipate, and would not allow, crucial
experiments to point in the direction of
any single hypothesis. In this it distinguishes
itself from the classic analytic method,
which, in its ideal representation, requires
(a) an exhaustive set of hypotheses and
(b) a decisive falsification of all but one of
these. In ecology, both conditions are diffi-
cult to meet in practice and, arguably, by its
own construction, this method discourages
synthesis and a consideration of multiple
effects.

On the cultivation and invention of knowl-
edge. Although it is not convenient here to
be dogmatic about affiliations between po-

sitions in philosophy and positions in statistics, null-hypothesis
testing is clearly based on Bacon’s systematic method of in-
ductive reasoning and decisive falsification of hypotheses
(Platt 1964). Yet Bacon did not intend that the method of “the
interpretation of nature” be the whole truth, but rather only
one part of it:

Let there be therefore (and may it be for the benefit of
both) two streams and two dispensations of knowledge,
and in like manner two tribes or kindreds of students in
philosophy—tribes not hostile or alien to each other,
but bound together by mutual services; let there in
short be one method for the cultivation, another for the
invention, of knowledge. (Bacon 1620)

An initial interpretation might be that Bacon is describing
the difference between science and nonscience. To the con-
trary, Bacon emphasizes that by the method of inductive
reasoning, one may discover and demonstrate new knowledge
in both the sciences and the arts (Platt 1964). This broader
notion of science is accorded cultural universality by Colin
Scott:

If one means by science a social activity that draws
deductive inferences from first premises, that these
inferences are deliberately and systematically verified in
relation to experience, and that models of the world are
reflexively adjusted to conform to observed regularities
in the course of events, then, yes, Cree hunters practice

Figure 2. Two possible pathways to inference in ecological systems: (a) simple
experimental design and (b) observational study.

www.biosciencemag.org July/August 2007 / Vol. 57 No. 7 • BioScience 611

Thinking of Biology

Thinking of Biology

science—as surely as all human societies do.
(Scott 1996)

Scott refers not only to the testing of knowledge by way of
experience but also to the adjustment of models of the world.
This is a critical observation because it recognizes that there
is much more to the process of science than is contained
solely in Bacon’s method for the invention of knowledge.
Science includes the synthesis of different kinds of knowledge
into consistent structures, and the use of imagination in de-
veloping explanations to account for our observations of the
world. Some people call this critical or lateral thinking, and
it is fundamental to all scientific disciplines. This is impor-
tant because the greatest value of Chamberlin’s MMWH
(and also Bradford-Hill’s guidelines for inferring causation)
lies in the construction of hypotheses and the testing of com-
plex systems in settings where explanations are not necessarily
mutually exclusive.

Truth, null-hypothesis testing, and model selection. The
notion of truth, in its various guises, is integral to the way dif-
ferent philosophers of science have approached the concept
of hypothesis testing. However, pragmatic individuals (in-
cluding most scientists) find it more convenient simply to get
on with the job at hand, rather than to philosophize about such
nebulous matters. So why consider it at all? We suggest two
practical reasons: First, because good scientific method relies
on the proper construction and testing of hypotheses, in-
cluding the concept of falsification; second, because the way
scientists justify their ability to make inferences from data is
mediated by the branch of mathematics known as probabil-
ity theory. It is here that notions of absolute and relative (or
probabilistic) truth gain heightened importance in the way
that we present data and derive our conclusions.

All methods of scientific inference place great importance
on the proper construction of hypotheses in order to better
approach the true state of nature. But in the classic analytic
method, these hypotheses cannot, in fact, overlap in their de-
sign or content, because they need to be logically or statisti-
cally distinguishable from each other. Similarly, null-hypothesis
testing requires that there be a defined condition that a hy-
pothesis may or may not fulfill, and falsification consists of
disproving hypotheses that are shown to be inconsistent with
this existent truth (Anderson et al. 2000). Furthermore, these
alternative hypotheses are not directly tested in any way—
support is engendered by rejecting the null, and then infer-
ring a plausible explanation. The Bayesian information cri-
terion (BIC) is a dimension-consistent form of model selection
intended to provide a measure of the weight of evidence
favoring one model over another (the Bayes factor). The
target of the BIC is the “true model,” under the assumption
that it is included in the model set under consideration. As
the sample size becomes larger, the BIC approaches the esti-
mation of the dimension of this true model with a probability
of 1 (Burnham and Anderson 2004). In stark contrast, model
selection based on information theory (usually applied using

Akaike’s information criterion, or AIC) immediately states that
all models are in fact false, because they represent incomplete
approximations of a real but unreachable truth.

As an approximation of Kullback-Leibler information,
AIC model selection weights models in accordance with their
fit to the observed data, and represents the relative distances
between conceptual reality and a set of approximating mod-
els (Burnham and Anderson 2002). Parsimony (essentially, Oc-
cam’s razor) is reinforced as a result of the correction for
asymptotic bias. In appraising simultaneously how different
models fit with observed data based on “predictive likeli-
hood” (i.e., out-of-sample prediction), a picture is devel-
oped that is less susceptible to the idea that a single model is
in fact “true” (Burnham and Anderson 2004)—recall Cham-
berlin’s description of the single working hypothesis. We ar-
gue that this position is more compatible with Chamberlin’s
position, and that the different philosophical basis of AIC
model selection becomes a practical asset when assessing
complex systems. The information-theoretic approach also
drives the evolution of scientific hypotheses, because through
repeated exposure to new data, hypotheses or models lack-
ing any empirical support can be dropped, hypotheses re-
maining may be further refined, and new hypotheses will be
derived and added to the working set.

This is not to suggest (as others have) that null-hypothe-
sis testing methods should not be used. Despite the many ar-
ticles written justly decrying the inappropriate use of P values
(Carver 1978, Johnson 2002), there is nothing actually in-
correct about using null-hypothesis testing methods to make
inferences, and we do not propose to argue otherwise (see
Stephens et al. [2005] for a recent discussion). It is simply that
P values do not represent a proper “strength of evidence”
(Lukacs et al. 2007). Yet there is a greater natural concordance
(and potentially greater efficiency and economy of thought)
between AIC model selection and the MMWH, and conversely
between null-hypothesis testing, BIC model selection, and the
classic analytic method. This may not, however, be a straight-
forward relationship; for instance, the MMWH in parallel (fig-
ure 1b) may be more suited to the use of AIC model selection
than the more conceptual MMWH in series (figure 1a).

With the exponential rise in computing power, other al-
ternative but numerically intensive paradigms, such as cross-
validation and full Bayesian inference (not BIC), are being used
more frequently in ecology (Turchin 2003, Clark 2005). A
Bayesian definition of probability includes the degree of
belief in an event or model, an approach that enables greater
flexibility when evaluating data from complex or incomplete
data sets. With regard to Chamberlin’s MMWH, Bayesian
methods, like AIC model selection, have the distinct advan-
tage of removing one’s reliance on the literal falsification of
competing hypotheses; they also allow for an explicit in-
corporation of uncertainty in the modeling process and in the
accumulation of knowledge. It has been suggested that this
shift toward alternative methods of inference has occurred
primarily for pragmatic reasons (Stephens et al. 2005). We
argue that a shift in philosophical position may be a natural

612 BioScience • July/August 2007 / Vol. 57 No. 7 www.biosciencemag.org

outcome of these recent developments. This has implica-
tions not only for the way that scientists consider the use of
statistics when we make inferences about the world, but also
for the way that science defines itself in relation to other
kinds of knowledge.

Applications of Chamberlin’s method and multimodel infer-
ence. Model selection has been readily adopted in some
areas of biology, especially wildlife management (e.g.,
capture–mark–recapture analysis to determine the interplay
of intrinsic and environmental influences on survival and den-
sity), population ecology (e.g., establishing the relative plau-
sibility of cyclic versus chaotic dynamics in long-term time
series), and, increasingly, conservation biology (e.g., deter-
mining which anthropogenic factors best predict range de-
clines in threatened species; for details on these and other
biological examples, see Buckland et al. 1997, Hilborn and
Mangel 1997, Morris and Doak 2002, Turchin 2003, Johnson
and Omland 2004). A primary motivation for the application
of model selection in these fields is the separation of biolog-
ically important signals from the myriad of “tapering ef-
fects” that characterize full truth but defy reductionism. An
additional intellectual step, in particular harmony with se-
quential and simultaneous multiple working hypotheses (fig-
ure 1), is to invoke the concept of multimodel inference
(MMI; Burnham and Anderson 2002). Rather than selecting
a single “best” model, MMI involves making inferences on the
basis of all models in an a priori candidate set, with the
weighted contribution of each model (hypothesis) governed
by its relative support from the data (estimated using scaled
differences in AIC [AIC weights] or Bayesian posterior prob-
abilities). MMI has three clear advantages: (1) It accounts ex-
plicitly for uncertainty in choosing the Kullback-Leibler best
model (e.g., due to finite sample size), (2) it permits inference
from different models that may be concurrently true (to
lesser or greater extents), and (3) it allows researchers to es-
timate unconditional measures of precision and of the rela-
tive importance of variables.

A key example serves to illustrate these benefits. A long-
standing debate has raged in population ecology over the ap-
propriate means to detect intrinsic regulation (density
dependence) in abundance time series (summarized in Brook
and Bradshaw 2006). The classic approach has been to apply
various significance tests, on a case-by-case basis, and eval-
uate whether there is sufficient evidence to reject a null model
of density independence at α = 0.05. But why, when there ex-
ists ample mechanistic evidence for the action of density
feedbacks on survival and reproductive rates (Osenberg et al.
2002), should the null model be so favored? At the very least,
the “competing” hypotheses of density independence versus
density dependence should be evaluated on equal starting
terms (a Bayesian might argue for strongly favoring density
dependence a priori). Brook and Bradshaw (2006) used
model selection to do this for time series covering 1198
species, and showed density dependence to be the better-
supported hypothesis in 75 to 92 percent of cases, compared

with 33 to 50 percent for null-hypothesis testing. But perhaps
more important, there were many instances in which there was
reasonable strength of evidence for both hypotheses accord-
ing to AIC, even for long-monitored populations with high
statistical power. This supports a philosophical stance in
which the question is not “Does density dependence occur in
this population?” (in the broad sense of the classic analytic
model), but rather “What is the relative importance of density-
independent (extrinsic) and density-dependent (intrinsic)
processes in driving the dynamics of this population?” This
latter is a richer and more biologically meaningful line of in-
quiry, and more closely allied with the spirit of both MMI and
Chamberlin’s MMWH.

Conclusions
Western science and philosophy have a long tradition of
thought concerned explicitly with the notions of observation,
inference, truth, and prediction. Yet the statistical methods that
we would recognize today are less than 100 years old. This
raises a question: What were Hooke, Linnaeus, Cuvier, and
Darwin doing before the development of the P value? Their
substantial contributions to biology remind us that analytic
thought is only one component of science. We posit that be-
cause null-hypothesis testing has been established as ortho-
dox practice, the core meaning of Chamberlin’s MMWH
has been lost or altered. It now takes on even greater value than
it had before, because it describes explicitly the processes of
synthetic thought useful for approaching complexity, a timely
concept for the application of 21st-century statistics.

Hilborn and Mangel (1997) liken the study of ecology to
the investigations of a detective, whereby a coherent picture
must be built up from an array of small and varied clues. It
is no coincidence that Chamberlin’s MMWH drew from a
similar quarter—the field of geology—where it is difficult (and
often inappropriate) to separate confounding variables using
a series of dichotomous tests against a null. In fact there is a
spectrum of possible approaches to analyses in natural science,
from repeatable experimental designs with controlled treat-
ments to diachronic observational studies in which the lux-
ury of control is simply not tenable (Stephens et al. 2005).
Chamberlin (1890) espouses a worldview that values lateral
thinking and multiple possibilities. This can only be a posi-
tive development in a world where religious and political
fundamentalism represents complexity in a black-and-white
fashion. It seems appropriate that we revisit these ideas at such
a time in history.

Acknowledgments
We thank Daniel Banfai for numerous suggestions, and for
help in preparing figure 1; David Bowman for prompting
thought on how our ideas link to the Bradford-Hill guidelines;
and three anonymous referees for their especially detailed and
helpful comments on earlier drafts.

Thinking of Biology

www.biosciencemag.org July/August 2007 / Vol. 57 No. 7 • BioScience 613

614 BioScience • July/August 2007 / Vol. 57 No. 7 www.biosciencemag.org

References cited
Anderson DR, Burnham KP. 2002. Avoiding pitfalls when using information–

theoretic methods. Journal of Wildlife Management 66: 912–918.
Anderson DR, Burnham KP, Thompson WL. 2000. Null hypothesis testing:

Problems, prevalence, and an alternative. Journal of Wildlife Management
64: 912–923.

Bacon F. 1620. The New Organon, or True Directions Concerning the
Interpretation of Nature. (11 May 2007; www.constitution.org/bacon/
nov_org.htm)

Bradford-Hill A. 1966. The environment and disease: Association or
causation? Proceedings of the Royal Society of Medicine 58: 295–300.

Brook BW, Bradshaw CJA. 2006. Strength of evidence for density dependence
in abundance time series of 1198 species. Ecology 87: 1445–1451.

Buckland ST, Burnham KP, Augustin NH. 1997. Model selection: An
integral part of inference. Biometrics 53: 603–618.

Burnham KP, Anderson DR. 2002. Model Selection and Multi-model
Inference: A Practical Information-Theoretic Approach. New York:
Springer.

———. 2004. Understanding AIC and BIC in model selection. Sociologi-
cal Methods and Research 33: 261–304.

Carver RP. 1978. The case against statistical significance testing. Harvard
Educational Review 48: 378–399.

Chamberlin TC. 1890. The method of multiple working hypotheses. Science
15: 92–96 (reprinted in Science 148: 754–759 [1965]).

Clark JS. 2005. Why environmental scientists are becoming Bayesians.
Ecology Letters 8: 2–14.

Fisher AC Jr. 1980. My Chesapeake—Queen of Bays. National Geographic
158: 428–467.

Hilborn R, Mangel M. 1997. The Ecological Detective: Confronting
Models with Data. Princeton (NJ): Princeton University Press.

Johnson DH. 2002. The role of hypothesis testing in wildlife science.
Journal of Wildlife Management 66: 272–276.

Johnson JB, Omland KS. 2004. Model selection in ecology and evolution.

Trends in Ecology and Evolution 19: 101–108.

Lukacs PM, Thompson WL, Kendall WL, Gould WR, Doherty PF, Burnham

KP, Anderson DR. 2007. Concerns regarding a call for pluralism of

information theory and hypothesis testing. Journal of Applied Ecology

44: 456–460.

McBride GB, Loftis JC, Adkins NC. 1993. What do significance tests really

tell us about the environment? Environmental Management 17: 423–432.

Morris WF, Doak DF. 2002. Quantitative Conservation Biology: Theory

and Practice of Population Viability Analysis. Sunderland (MA): Sinauer.

Osenberg CW, St. Mary CM, Schmitt RJ, Holbrook SJ, Chesson P, Byrne B.

2002. Rethinking ecological inference: Density dependence in reef fishes.

Ecology Letters 5: 715–721.

Phillips CV, Goodman KJ. 2004. The missed lessons of Sir Austin Bradford

Hill. Epidemiological Perspectives and Innovations 1: 3. (4 June 2007;

www.epi-perspectives.com/content/1/1/3)

Platt JR. 1964. Strong inference. Science 146: 347–353.

Scott C. 1996. Science for the West, myth for the rest? Pages 69–86 in Nader

L, ed. Naked Science: Anthropological Inquiry into Boundaries, Power,

and Knowledge. New York: Routledge.

Stephens PA, Buskirk SW, Hayward GD, Martinez del Rio C. 2005.

Information theory and hypothesis testing: A call for pluralism. Journal

of Applied Ecology 42: 4–12.

Turchin P. 2003. Complex Population Dynamics: A Theoretical/Empirical

Synthesis. Princeton (NJ): Princeton University Press.

Wade PR. 2000. Bayesian methods in conservation biology. Conservation

Biology 14: 1308–1316.

doi:10.1641/B570708
Include this information when citing this material.

Thinking of Biology

The Method of Multiple
Working Hypotheses

With this method the dangers of parental
affection for a favorite theory can be circumvented.

T. C. Chamberlin

As methods of study constitute the
leading theme of our session, I have
chosen as a subject in measurable con-
sonance the method of multiple work-
ing hypotheses in its application to
investigation, instruction, and citizen-
s h i p .

There are two fundamental classes
of study. The one consists in attempt-
i n g to follow by close imitation the
processes of previous thinkers, or to
acquire by memorizing the results of
their investigations. It is merely sec-
ondary, imitative, or acquisitive study.
The other class is primary or creative
study. In it the effort is to think in-
dependently, or at least individually, in
the endeavor to discover new truth,
or to make new combinations of truth,
or at least to develop an individualized
aggregation of truth. The endeavor is
to think for one’s self, whether the
thinking lies wholly in the fields of
previous thought or not. It is not neces-
sary to this habit of study that the sub-
ject-material should be new; but the
process of thought and its results must
be individual and independent, not the
mere following of previous lines of
thought ending in predetermined re-
s&s. The demonstration of a nroblem

Thomas C. Chamberlin (1843-1928). a geologist,
was president of the University of Wisconsin at
the time this lecture was written. Later he was
professor and director of the Walker Museum of
the University of Chicago. In 1893 he founded
the Journal of Geology, which he edited until
his death. In 1908 he was president of the AAAS.
The article is reprinted from Science (old series),
15, 92 (1890).

Reprints of this article are available.
P r i c e s ( c a s h w i t h o r d e r ) :

1 50 cents (or 25 cents and stamped,
self-addressed envelope)

2 to 9 45 cents each
IO to 24 30 cents each
2 5 o r m o r e 20 cents each

Address orders to AAAS, Chamberlin Reprints,

151

5 Massachusetts Ave., NW, Washington, D.C.
2 0 0 0 5 .

154

in Euclid precisely as laid down is an
illustration of the former; the demon-
stration of the same proposition by a
merhod of one’s own or in a manner
distinctively individual is an illustration
of the latter; both lying entirely within
the realm of the known and the old.

Creative study, however, finds its
largest application in those subjects in
which, while much is known, more re-
mains to be known. Such are the fields
which we, as naturalists, cultivate: and
we are gathered for the purpose of
developing improved methods lying
largely in the creative phase of study,
t h o u g h n o t w h o l l y s o .

Intellectual methods have taken three
phases in the history of progress thus
far. What may be the evolutions of
the future it may not be prudent to
forecast. Naturally the methods we now
urge seem the highest attainable. These
three methods may be designated, first,
the method of the ruling theory; sec-
ond, the method of the working hypoth-
esis; and, third, the method of mul-
t i p l e w o r k i n g h y p o t h e s e s .

In the earlier days of intellectual de-
velopment the sphere of knowledge
was limited, and was more nearly with-
in the compass of a single individual;
and those who assumed to be wise
men, or aspired to be thought so, felt
the need of knowing, or at least seem-
ing to know, all that was known as a
justification of their claims. So, also,
there grew up an expectancy on the
part of the multitude that the wise and
the learned would explain whatever
new thing presented itself. Thus pride
and ambition on the one hand, and
expectancy on the other, developed the
putative wise man whose knowledge
boxed the compass, and whose acumen

found an explanation for every new
puzzle which presented itself. This dis-
position has propagated itself, and has
come down to our time as an intellec-
tual predilection, though the compass-
ing of the entire horizon of knowledge
has long since been an abandoned af-
fectation. As in the earlier days, so
still, it is the habit of some to hastily
conjure up an expIanation for every
new phenomenon that presents itself.
Interpretation rushes to the forefront
as the chief obligation pressing upon
the putative wise man. Laudable as the
effort at explanation is in itself, it is
to be condemned when it runs before
a serious inquiry into the phenomenon
itself. A dominant disposition to find
out what is, should precede and crowd
aside the question, commendable at a
later stage, “How came this so?” First
full facts, then interpretations.

Premature Theories

The habit of precipitate explanation
leads rapidly on to the development of
tentative theories. The explanation of-
fered for a given phenomenon is nat-
urally, under the impulse of self-con-
sistency, offered for like phenomena as
they present themselves, and there is
soon developed a general theory ex-
planatory of a large class of phenom-
ena similar to the original one. This
general theory may not be supported
by any further considerations than
those which were involved in the first
hasty inspection. For a time it is likely
to be held in a tentative way with a
measure of candor. With this tentative
spirit and measurable candor, the mind
satisfies its moral sense, and deceives
itself with the thought that it is pro-
ceeding cautiously and impartially to-
ward the goal of ultimate truth. It
fails to recognize that no amount of
provisional holding of a theory, so long
as the view is limited and the investi-
gation partial, justifies an ultimate con-
v i c t i o n . It is not the slowness with
which conclusions are arrived at that
should give satisfaction to the moral
sense, but the thoroughness, the com-
pleteness, the all-sidedness, the impar-
tiality, of the investigation.
It is in this tentative stage that the

affections enter with their blinding in-
fluence. Love was long since represent-
ed as blind, and what is true in the
personal realm is measurably true in
the intellectual realm. Important s,;.,

SCIENCE: VOL. 148.j

: +he intellectual affections are as stimuli
I – –

and a s r e w a r d s , they are nevertheless
dangerous f a c t o r s , w h i c h m e n a c e t h e
integrity of the intellectual processes.
The moment one has offered an origi-
nal e x p l a n a t i o n f o r a p h e n o m e n o n
which seems satisfactory, that moment
affection f o r h i s i n t e l l e c t u a l c h i l d
springs into existence; and as the ex-
planation grows into a definite theory,
hi‘; parental affections cluster about his
int~l[ectLlZll offspring, and it grows more
and more dear to him, so that, while
he h o l d s i t s e e m i n g l y t e n t a t i v e , i t i s
s t i l l l o v i n g l y t e n t a t i v e , a n d n o t i m –
partially tentative. So soon as this pa-
rcnt;ll affection takes possession of the
mincl. there is a rapid passage to the
a d o p t i o n o f t h e t h e o r y . T h e r e i s a n
unconscious selection and magnifying
of the p h e n o m e n a t h a t f a l l i n t o h a r –
mony with the theory and support it.
and a n u n c o n s c i o u s n e g l e c t o f t h o s e
t h a t f a i l o f c o i n c i d e n c e . T h e m i n d
lingers w i t h p l e a s u r e u p o n t h e f a c t s
that f a l l h a p p i l y i n t o t h e e m b r a c e o f
the t h e o r y , a n d f e e l s a n a t u r a l cold-
nc,s toward those that seem refractory.
Instinctively there is a special se:lrch-
ing-out of phenomena that support it.
for the mind is led by its desires.
There springs up, also, an unconscious
pressing of the theory to make it fit
the facts, and a pressing of the facts
t o m a k e t h e m f i t t h e t h e o r y . W h e n
these biasing tendencies set in, the mind
rapidly degenerates into the partiality
of paternalism. The search for facts,
the observation o f p h e n o m e n a and
their interpretation, are all dominated
hy affection for the favored theory un-
til it appears to its author or its advo-
c:lle to have been overwhelmingly es-
tablished. The theory then rapidly rises
to the ruling’. position. and investiga-
tion. observation, and interpretation are
c o n t r o l l e d a n d d i r e c t e d b v i t . F r o m
an (Induly favored child, it- readily be-
Conies master, and leads its au-
thor whithersoever it will. The subse-
quent history of that mind in respect
to t h a t t h e m e i s b u t t h e p r o g r e s s i v e
dominance of a ruling idea.

Briefly summed up. the evolution is
this: a p r e m a t u r e e x p l a n a t i o n p a s s e s
into a tentative theory, t h e n i n t o a n
adopted theory, and then into a ruling
t h e o r y .

M’hen the last stage has been
reached. u n l e s s t h e t h e o r y h a p p e n s ,
perchance, to be the true one, all hope

results is gone. To be sure,
y be brought forth by an in-

Thomas Chrowder Chamberlin was noted
for his contributions to glaciology and for
his part in formulating the Chamberlin-
Moulton (planetesimal) hypothesis of the
origin of the earth.

vestigator dominated by a false ruling
idea. His very errors may indeed stimu-
late investigation on the part of oth-
ers. But the condition is an unfortu-
nate one. Dust and chaff are mingled
w i t h t h e g r a i n i n w h a t s h o u l d b e a
winnowing process.

Ruling Theories Linger

As previously implied, the method of
t h e r u l i n g t h e o r y o c c u p i e d a c h i e f
place during the infancy of investiga-
tion. It is an expression of the natural
infantile tendencies of the mind, though
in this case applied to its higher ac-
tivities, for in the earlier stages of de-
v e l o p m e n t t h e f e e l i n g s a r e r e l a t i v e l y
greater than in, later stages.

Unfortunately it did not wholly pass
away with the infancy of investigation,
but has lingered along in individual in-
stances to the present day, and finds
illustration in universally learned men
and pseudo-scientists of our time.

The defects of the method are obvi-
ous, and its errors great. If I were to
name the central psychological fault, I
should say that it was the admission
o f i n t e l l e c t u a l a f f e c t i o n t o t h e p l a c e
that should be dominated by impartial
intellectual rectitude.

SO long as intellectual interest dealt
chiefly with the intangible, so long it
was possible for this habit of thought

to survive, and to maintain its domi-
n a n c e , b e c a u s e t h e p h e n o m e n a t h e m –
selves, being largely subjective, were
plastic in the hands of the ruling idea;
but so soon as investigation turned it-
self earnestly to an inquiry into nat-
ural phenomena, whose manifestations
are tangible, w h o s e p r o p e r t i e s a r e
rigid, whose laws are rigorous, the de-
fects of the method became manifest,
a n d a n e f f o r t a t r e f o r m a t i o n e n s u e d .
T h e f i r s t g r e a t e n d e a v o r w a s r e p r e s –
sive. The advocates of reform insisted
t h a t t h e o r i z i n g s h o u l d b e r e s t r a i n e d ,
and efforts directed to the simple de-
termination of facts. The effort was to
make scientific study factitious instead
of causal. Because theorizing .in narrow
lines had led to manifest evils, theorizing
was to be condemned. The reformation
urged was not the proper control and
utilization of theoretical effort, but its
s u p p r e s s i o n . W e d o n o t n e e d t o g o
backward more than twenty years to
find ourselves in the midst of this at-
tempted reformation. Its weakness lay
in its narrowness and its restrictive-
n e s s . T h e r e i s n o n o b l e r a s p i r a t i o n
of the human intellect than desire to
compass the cause of things. The dis-
position to find explanations and to
develop theories is laudable in itself.
It is only its ill use that is reprehensi-
ble. The vitality of study quickly dis-
a p p e a r s w h e n t h e o b j e c t s o u g h t i s a
mere collocation of dead unmeaning
facts.

The inefficiency of this simply re-
pressive reformation becoming appar-
e n t , i m p r o v e m e n t w a s s o u g h t i n t h e
m e t h o d o f t h e w o r k i n g h y p o t h e s i s .
T h i s i s a f f i r m e d t o b e the s c i e n t i f i c
method of the day. but to this I take
exception. The working hypothesis dif-
fers from the ruling theory in that it
i s u s e d a s a m e a n s o f d e t e r m i n i n g
f a c t s , a n d h a s f o r i t s c h i e f f u n c t i o n
the suggestion of lines of inquiry; the
inquiry being made, not for the sake
of the hypothesis, but for the sake of
f a c t s . U n d e r t h e m e t h o d o f t h e r u l –
ing theory, the stimulus was directed
to the finding of facts for the support
o f t h e t h e o r y . U n d e r t h e w o r k i n g
hypothesis, t h e f a c t s a r e s o u g h t f o r
the purpose of ultimate induction and
demonstration, t h e h y p o t h e s i s b e i n g
b u t a m e a n s f o r t h e m o r e r e a d y d e –
velopment of facts and of their rela-
tions, and the arrangement and preser-
v a t i o n o f m a t e r i a l f o r t h e f i n a l i n –
duction.

It will be observed that the disiinc-

tion is not a sharp one, and that a
working hypothesis may with the ut-
most ease degenerate into a ruling
theory. Affection may as easily cling
about an hypothesis as about a the-
o r y , and the demonstration of the
one may become a ruling passion as
much as of the other.

A Family of Hypotheses

Conscientiously followed, the meth-
od of the working hypothesis is a
marked improvement upon the method
of the ruling theory; but it has its de-
fects-defects which are perhaps best
expressed by the ease with which the
hypothesis becomes a controlling idea.
To guard against this, the method of
multiple working hypotheses is urged.
It differs from the former method in
the multiple character of its genetic
conceptions and of its tentative inter-
pretations. It is directed against the
radical defect of the two other meth-
ods; namely, the partiality of intellec-

. tual parentage. The effort is to bring
up into view every rational explana-
tion of new phenomena, and to de-
velop every tenable hypothesis respect-

-ing their cause and history. The in-
vestigator thus becomes the parent of
a family of hypotheses: and, by his
parental relation to all, he is forbidden
to fasten his affections unduly upon
any one. In the nature of the case, the
danger that springs from affection is
counteracted, and therein is a radical
difference between this method and the
two preceding. The investigator at the
outset puts himself in cordial sympathy
and in parental relations (of adoption,
if not of authorship) with every hy-
pothesis that is at all applicable to the
case under investigation. Having thus
neutralized the partialities of his emo-
tional nature, he proceeds with a cer-
tain natural and enforced erectness of
mental attitude to the investigation,
knowing well that some of his
tellectual children will die before ma-
turity, yet feeling that several of them
may survive the results of final in-
vestigation, since it is often the out-
come of inquiry that several causes
are found to be involved instead of a
single one. In following a single hy-
pothesis, the mind is presumably led
to a single explanatory conception. But
an adequate explanation often involves
the co-ordination of several agencies,
which enter into the combined result

7 5 6

in varying proportions. The true ex-
planation is therefore necessarily com-
plex. Such complex explanations of
phenomena are specially encouraged by
the method of multiple hypotheses,
and constitute one of its chief merits.
We are so prone to attribute a phe-
nomenon to a single cause, that, when
we find an agency present, we are lia-
ble to rest satisfied therewith, and fail
to recognize that it is but one factor,
and perchance a minor factor, in the
accomplishment of the total result.
Take for illustration the mooted ques-
tion of the origin of the Great Lake
basins. We have this, that, and the
other hypothesis urged by different stu-
dents as the cause of these great ex-
cavations; and all of these are urged
with force and with fact, urged justly
to a certain degree. It is praclically
demonstrable that these basins were
river-valleys antecedent to the glacial
incursion, and that they owe their ori-
gin in part to the pre-existence of those
valleys and to the blocking-up of their
outlets. And so this view of their origin
is urged with a certain truthfulness.
So, again, it is demonstrable that they
were occupied by great lobes of ice,
which excavated them to a marked
degree, and therefore the theory of
glacial excavation finds support in fact.
I think it is furthermore demonstrable
that the earth’s crust beneath these
basins was flexed downward, and that
they owe a part of their origin to
crust deformation. But to my judg-
ment neither the one nor the other,
nor the third, constitutes an adequate
explanation of the phenomena. All
these must be taken together, and pos-
sibly they must be supplemented by
other agencies. The problem, there-
fore, is the determination not only of
the participation, but of the measure
and the extent, of each of these agen-
cies in the production of the complex
result. This is not likely to be ac-
complished by one whose working hy-
pothesis is pre-glacial erosion, or gla-
cial erosion, or crust deformation, but
by one whose staff of working hy-
potheses embraces all of these and any
other agency which can be rationahy
conceived to have taken part in the
p h e n o m e n a .

A special merit of the method is,
that by its very nature it promotes
thoroughness. The value of a working
hypothesis lies largely in its suggestive-
ness of lines of inquiry that might
otherwise be overlooked. Facts that are

trivial in themselves are brought into
significance by their bearings upon
the hypothesis, and by their causal in-
dications. As an illustration, it is only
necessary to cite the phenomenal in-
fluence which the Darwinian hypothe-
sis has exerted upon the investigations
of the past two decades. But a single
working hypothesis may lead investiga-
tion along a given line to the neglect of
others equally important; and thus,
while inquiry is promoted in certain
q u a r t e r s , the investigation lacks in
completeness. But if all rational hy-
potheses relating to a subject are
worked co-equally, thoroughness is the
presumptive result, in the very nature
of the case.

In the use of the multiple method,
the re-action of one hypothesis upon
another tends to amplify the recog-
nized scope of each, and their mutual
conflicts whet the discriminative edge
of each. The analytic process, the de-
velopment and demonstration of crite-
ria, and the sharpening of discrimina-
tion, receive powerful impulse from
the co-ordinate working of several
h y p o t h e s e s . r

FertiIity in processes is also the natu-
r a l o u t c o m e o f t h e m e t h o d . E a c h
hypothesis suggests its own criteria,
its own means of proof, its own meth-
ods of developing the truth; and if a
group of hypotheses encompass the
subject on all sides, the total outcome
of means and of methods is full and
rich.

The use of the method leads to cer-
tain peculiar habits of mind which
deserve passing notice, since as a fat:
tor of education its disciplinary value
is one of importance. When faithfully
pursued for a period of years, it de-
velops a habit of thought anaIogous to
the method itself, which may be des-
ignated a habit of parallel or complex
thought. Instead of a simple succes-
sion of thoughts in linear order, the
procedure is complex, and the mind
appears to become possessed of the
power of simultaneous vision from dif-
ferent standpoints. Phenomena appear
to become capable of being viewed
anaIyticaIly and synthetically at once.
It is not altogether unlike the study
o f a l a n d s c a p e , f r o m w h i c h t h e r e
comes into the mind myriads of lines
of intelligence, which are received and
co-ordinated simultaneously, producing
a complex impression which is re-
corded and studied directly in its corn-
plexity. My description of this process

SCIENCE, VOL. 148

T. C. Chamberlin published two papers under the title of “The method of multiple working
hypotheses.” One of these papers, first published in the Journal of Geology in 1897, was quoted
by John R. Platt in his recent article “Strong inference” (Science, 16 Oct. 1964). Platt wrote:
“This charming paper deserves to be reprinted.” Several readers, having had difficulty obtain-
ing copies of Chamberlin’s paper, expressed agreement with Platt. One wrote that the article
bad been reprinted in the Journal of Geology in 1931 and in the Scientific Monthly in Novem-
ber 1944. Another sent us a photocopy. Several months later still another wrote that the Insti-
tute for Humane Studies (Stanford, Calif.) had reprinted the article in pamphlet form this year.
(>n consulting the 1897 version, we found a footnote in which Chamberlin had written: “A paper
on this subject was read before the Society of Western Naturalists in 1892, and was published in
a scientific periodical.” Library research revealed that “a scientific periodical” was Science it-
self, for 7 February 1890, and that Chamberlin had actually read the paper before the Society
of Western Naturalists on 25 October 1889. The chief difference between the 1890 text and the
1897 text is that, as Chamberhn wrote in 1897: “The article has been freely altered and abbrevi-
ated so as to limit it to aspects related to geological study.” The 1890 text, which seems to be
the first and most general version of “The method of multiple working hypotheses,” is reprinted
here. Typographical errors have been corrected, and subheadings have been added.

Is confessedly inadequate, and the af-
firmation of it as a fact would doubt-

less challenge dispute at the hands of
psychologists of the old school; but 1
address myself to naturalists who I

.: think can respond to its verity from
” their own experience.

Drawbacks of the Method.,

The method has, however, its dis–_
advantages. No good thing is without
: its drawbacks; and this very habit of

mind, while an invaluable acquisition
for purposes of investigation. intro-
duces difficulties in expression. It iS
obvious, upon consideration, that this
method of thought is impossible of
verbal expression. We cannot put into
w o r d s m o r e t h a n a s i n g l e l i n e o f
thought at the same time; and even in
that the order of expression must be
conformed to the idiosyncrasies of the

’ language, and the rate must be rela-
tively slow. When the habit of complex

: thought is not highly developed, there
is usually a leading line to which others

i are subordinate, and the difficulty of
! expression does not rise to serious pro-
$ Portions; but when the method of
z Shultaneous v i s i o n along different
i lines is developed so that the thoughts
‘i, running
0

i n d i f f e r e n t channeIs a r e

&
nearly equivalent, there is an obvious
embarrassment in selection and a dis-
nclination to make the attempt. Fur-
thermore, the impossibility of express-
ing the mental operation in words leads

tn their disuse in the silent process of
‘) I,… .̂ ._

thought, and hence words and thoughts
lose that close association which they
are accustomed to maintain with those
whose silent as well as spoken thoughts
run in linear verbal courses. There is
therefore a certain predisposition on
the part of the practitioner of this
method to taciturnity.

We encounter an analogous diffi-
culty in the use of the method with
young students. It is far easier, and I
think in general more interesting, for
them to argue a theory or accept a
simple interpretation than to recognize
and evaluate the several factors which
the true elucidation may require. To
illustrate: it is more to their taste to
be taught that the Great Lake basins
w-ere scooped out by glaciers than to
be urged to conceive of three or more
great agencies w-orking successively or
simultaneously, and to estimate how
much was accomplished by each of
these agencies. The comples and the
quantitative do not fascinate the young
student as they do the veteran investi-
g a t o r .

Multiple Hypotheses and

Practical Affairs

It has not been our custom to think
of the method of working hypotheses
as applicable to instruction or to the
practical affairs of life. We have USU-
ally regarded it as but a method of
science. But I believe its application
to practical affairs has a value CO-
ordinate with the importance of the

affairs themselves. I refer especially to
those inquiries and inspections that pre-
cede the coming-out of an enterprise
rather than to its actual execution. The
methods that are superior in scientific
investigation should likewise be SU-
perior in those investigations that are
the necessary antecedents to an in-
telligent conduct of affairs. But I can
dwell only briefly on this phase of
t h e s u b j e c t .

In education, as in investigation, it
has been much the practice to work
a theory. The search for instructional
methods has often proceeded on the
presumption that there is a definite
patent process through which all stu-
dents might be put and come out with
results of maximum excellence; and
hence pedagogical inquiry in the past
has very largely concerned itself with
the inquiry, “What is the best method?”
rather than with the inquiry, “What
are the special values of different
methods, and what are their several
advantageous applicabilities in the var-
ied work of instruction?” The past
doctrine has been largely the doctrine
of pedagogical uniformitarianism. But
the faculties and functions of the mind
are almost, if not quite, as varied as
the properties and functions of mat-
ter: and it is perhaps not less absurd
to assume that any specific method
of instructional procedure is more ef-
fective than all others, under any and
all circumstances, than to assume that
one principle o f i n t e r p r e t a t i o n is
equaIly applicable to all the phenom-
ena of nature. As there is an endless

151

variety of mental processes and combi-
nations and an indefinite number of
orders of procedure, the advantage of
different methods under different con-
ditions is almost axiomatic. This being
granted, t h e r e i s p r e s e n t e d t o t h e
teacher the problem of selection and
of adaptation to meet the needs of
any specific issue that may present
itself. It is important, therefore, that
the teacher shall have in mind a full
array of possible conditions and states
of mind which may be presented. in
order that, when any one of these
shall become an actual case. he may
recognize it, a n d b e r e a d y f o r t h e
e m e r g e n c y .

Just as the investigator armed with
many working hypotheses is more
likely to see the true nature and sig-
nificance of phenomena when they
present themselves, so the instructor
equipped with a full panoply of hy-
potheses ready for application more
readily recognizes the actuality of the
situation, more accurately measures its
s i g n i f i c a n c e , and more appropriately
applies the methods which the case
calls for.

The application of the method of
multiple hypotheses to the varied af-
fairs of life is almost as protean as
the phases of that life itself. but cer-
tain general aspects may be taken as
typical of the whole. What I have just
said respecting the application of the
method to instruction may apply. with
a simple change of terms, to almost
a n y o t h e r e n d e a v o r w h i c h w e a r e
called upon to undertake. We enter
upon an enterprise in most cases with-
out full knowledge of all the factors
that will enter into it, or all of the
possible phases which it may develop.
It is therefore of the utmost impor-
tance to be prepared to rightly compre-
hend the nature, bearings, and influ-
ence of such unforeseen elements when
they shall definitely present themselves
as actualities. If our vision is nar-
rowed by a preconceived theory as to
what will happen, we are almost cer-
tain to misinterpret the facts and to
misjudge the issue. If, on the other
hand, we have in mind hypothetical
forecasts of the various contingencies
that may arise, we shall be the more
l i k e l y t o r e c o g n i z e t h e t r u e f a c t s
when they do present themselves. In-
stead of being biased by the anticipa-
tion of a given phase, the mind is
rendered open and alert by the anti-
cipation of any one of many phases,
and is free not only, but is predisposed,

158

to recognize correctly the one which
does appear. The method has a further
good effect. The mind, having antici-
pated the possible phases which may
arise, has prepared itself for action
under any one that may come up, and
it is therefore ready-armed, and is pre-
disposed to act in the line appropriate
to the event. It has not set itself rigidly
in a fixed purpose, which it is pre-
disposed to follow without regard to
contingencies. It has not nailed down
the helm and predetermined to run a
specific course, whether rocks lie in
the path or not; but. with the helm
in hand, it is ready to veer the ship
according as danger or advantage dis-
c o v e r s i t s e l f .

It is true, there are often advantages
in pursuing a fixed predetermined
course without regard to obstacles or
adverse conditions. Simple dogged res-
olution is sometimes the salvation of
an enterprise: but, while glorious suc-
cesses have been thus snatched from
the very brink of disaster, overwhelm-
ing calamity has in other cases fol-
lowed upon this course, when a rea-
sonable regard for the unanticipated
elements would have led to success.
So there is to be set over against the
great achievements that follow on
zC-.gged <&?rrppp “rex disa,>iers which..~ -”
are equally its result.

Danger of Vacillation

The tendency of the mind, accus-
tomed to work through multiple hy-
potheses, is to sway to one line of pol-

o r a n o t h e r , according as t h e
balance of evidence shall incline. This
is the soul and essence of the method.
It is in general the true method. Never-
theless there is a danger that this yield-
ing to evidence may degenerate into
unwarranted vacillation. It is not al-
ways possible for the mind to balance
evidence with exact equipoise. and to
determine, in the midst of the execu-
t i o n o f a n e n t e r p r i s e , w h a t i s t h e
measure of probability on the one side
or the other: and as difficulties present
themselves, there is a danger of being
biased by them and of swerving from
the course that was really the true
one. Certain limitations are therefore
to be placed upon the application of
the method, for it must be remembered
that a poorer line of policy consistently
adhered to may bring better results
than a vacillation between better poli-
c i e s .

There is another and closely alli
d a n g e r in the application of t
method. In its highest deveiopment
presumes a mind supremely sensitive ,i”
to every grain of evidence. Like a pair+?
of delicately poised scales, every added’@:
particle on the one side or the other’%:
produces its effect in oscillation. But‘:
such a pair of scales may be altogether ‘,g
too sensitive to be of practical value%
in the rough affairs of life. The balancea
of the exact chemist are too delicate Z
for the weighing-out of coarse corn. ; I
modities. Despatch may be more im- ‘ ,
portant than accuracy. So it is possible’
for the mind to be too much con.
cerned with the nice balancings of evi-
dence, and to oscillate too much and
too long in the endeavor to reach
exact results. It may be better, in the
gross affairs of life, to be less precise
and more prompt. Quick decisions,
though they may contain a grain of
error, are oftentimes better than pre.
cise decisions at the expense of time.

The method has a special beneficent
application to our social and civic re.
lations. Into these relations there enter,
as great factors, our judgment of oth-
ers, our discernment of the nature of
their acts, and our interpretation of
their motives and purposes. The meth-
od of multiple hypotheses. in its an.
plicarion here, skifiifs in tieuied con-
t r a s t t o t h e m e t h o d o f t h e r u l i n g
theory or o f t h e s i m p l e w o r k i n g
hypothesis. The primitive habit is to
interpret the acts of others on the
basis of a theory. Childhood’s uncon- ~
scious theory is that the good are good,
and the bad are bad.’ From the good
the child expects nothing but good;
from the bad, nothing but bad. To ex-
pect a good act from the bad, or a
bad act from the good, is radically at
variance with childhood’s mental meth-
ods. Unfortunately in our social and
civic affairs too many of our fellow-
citizens have never outgrown the rul-
ing theory of their childhood.

Many have advanced a step farther,
and employ a method analagous to
that of the working hypothesis. A cer-
tain presumption is made to attach tn
the acts of their fellow-beings, and that
which they see is seen in the light of
that presumption, and that which they
construe is construed in the light of
that presumption. They do not go to
the lengths of childhood’s method by
assuming positively that the good are
wholly good, and the bad wholly bad;
but there is a strong presumption in
their minds that he concerning whom

SCIENCE. VOL. 148

hey have an ill opinion will act from
esponding motives. It requires pos-

dence to overthrow the it&t-
the working hypothesis.
ethod of multiple hypotheses

s b r o a d l y t h a t t h e a c t s o f a
being may be diverse in their

their moves, their purposes,
rice in their whole moral char-

ctcr; that they may be good though
dominant character be bad; that
may be bad though the dominant
cter be good; that they may be

od and partly bad, as is the
t i n t h e g r e a t e r n u m b e r o f t h e
plex activities of a human being.
er the method of multiple hypothe-

;; scs. it is the first effort of the mind to
,$ set truly what the act is, unbeclouded
! by the presumption that this or that

’ has hcen done because it accords with
: our r u l i n g t h e o r y o r o u r w o r k i n g

hypothesis. Assuming that acts of sim-
+ ihtr general aspect may readily take

;Iny one of several different phases,
the m i n d i s f r e e r t o s e e a c c u r a t e l y
what has actually been done. So, again.
in our interpretations of motives and

purposes, the method assumes that
these may have been any one of man>-.
;tad the first duty is to ascertain which

of possible motives and purposes ac-
tually prompted this individual action.
Going with this effort there is a pre-
disposition to balance all evidence

fairly, and to accept that interpreta-
tion to which the weight of evidence
inclines, not that which simply fits our
working hypothesis or our dominant
t h e o r y . T h e o u t c o m e , t h e r e f o r e , i s
better and truer observation and juster
and more righteous interpretation.

Imperfections of Knowledge

There is a third result of great im-
portance. The imperfections of our
knowledge are more likely to be de-
tected, for there will be less confidence
in its completeness in proportion as
there is a broad comprehension of the
possibilities of varied action, under
similar circumstances and with similar
appearances. So, also. the imperfec-
tions of evidence as to the motives
and purposes inspiring the action will
become more discernible in proportion
t o t h e fulness o f o u r c o n c e p t i o n o f
what the evidence should be to dis-
tinguish between action from the one
or the other of possible motives. The
necessary result will be a less disposi-
tion to reach conclusions upon im-
pe:fizc: groands. S o , a l s o , t h e r e w i l l
be a less inciination to misapply evi-
dence: for, several constructions be-
ing definitely in mind, the indices of
the one motive are less liable to be
mistaken for the indices of another.

Education as a Way of Life

Traditional arrangements for education must be
supplemented by a system designed for lifelong learning.

John W. Gardner

Nothing is more obsolete than the
notion that education is something that
takes place in a solid block of years
b e t w e e n . r o u g h l y , a g e s 6 a n d 2 2 .
From n o w o n ,
i n g

the individual is go-
10 have to seek formal instruction

at many points throughout his career.
Under such a system, much of the

Present anxiety over young people who

quit school prematurely will disappear.
The anxiety stems from the fact that
today leaving school signifies the end
of education. Under the new system
there will be no end to education.

Unfortunately, our institutional ar-
rangements for lifelong education are
ridiculously inadequate. Most educa-
tional institutions are still designed for

The total outcome is greater care in
ascertaining the facts, and greater dis-
crimination and caution in drawing
conclusions. I am confident, therefore,
that the general application of this
method to the affairs of social and civic
l i f e w o u l d g o f a r t o r e m o v e t h o s e
misunderstandings, misjudgments, and
misrepresentations which constitute so
pervasive an evil in our social and our
political atmospheres, the source of im-
measurable suffering to the best and
most sensitive souls. The misobserva-
tions, the misstatements, the misinter-
pretations, of life may cause less gross
suffering than some other evils; but
they, being more universal and more
subtle, pain. The remedy lies, indeed,
partly in charity, but more largely in
correct intellectual habits, in a pre-
dominant, ever-present disposition to
see things as they are, and to judge
them in the full light of an unbiased
weighing of evidence applied to all
possible constructions, accompanied by
a withholding of judgment when the
evidence is insufficient to justify con-
c l u s i o n s .

I believe that one of the greatest
moral reforms that lies immediately
before us consists in the general in-
troduction into social and civic life of
that habit of mental procedure which
is known in investigation as the method
of multiple working hypotheses.

young people who have nothing else
to do. They are ill suited to men
and women who must fit their learn-
ing into a busy life.

For years a small number of devoted
educators have sought to meet the
needs of this latter group, but they
have not received much cooperation
from the rest of the academic world.
That state of affairs appears to be
c h a n g i n g .

In the making now are some highly
flexible arrangements to make educa-
tion available to anyone able and will-
ing to learn, under circumstances suit-
ed to his needs. To indicate in con-
crete terms what such a system might
look like, I am going to describe cer-
tain activities of an imaginary univer-
sity-let us call it Midland State Uni-
versity. (It is not necessary that all
these activities be sponsored by a uni-
versity-a point which I discuss later.)

The a u t h o r i7 p r e s i d e n t o f C a r n e g i e Corporo-
t i o n o f N e w Y o r k . 5 8 9 F i f t h A v e n u e , N e w
Y o r k 10017.

159