International Journal o) Epidemiology
O International EpkJemtotogical Association 1996
Vol. 25, No. 4
Printed In Great Britain
Letter to the Editor
Atheoretical Science: A Response to the Poverty of Popperian
Epidemiology
From STEPHEN R COLE
Sir—In a recent edition of the Journal, the lead article
by Karhausen1 discusses the dangers of science falling
prey to dogmatism, using the example of Popperian
Epidemiology. The subject of scientific dogmatism has
long been at issue in the philosophy of science.2 I
commend the author on lighting the torch against doctrine, however one particular passage evokes a response. Karhausen states that there '... is little concern
in the epidemiologic literature with discovering laws of
nature and universal statements ...' Begrudgingly, I
agree. Epidemiology is a pragmatic empirical science,
with seemingly few minds attempting to derive theory
from fact, and literally no minds deriving law from
theory. This highly pragmatic viewpoint is clearly seen
in the analytical methods of epidemiology. By focusing
on disease in case-control design, or exposure in cohort
design, the emphasis of epidemiological study is clearly
on disease- or exposure-specific fact. Such an emphasis
has served the epidemiologist well. However, the benefit gained has carried cost. The cost is the clear lack of
attention to theory.
surely exist in epidemiology and medicine. Examples
do not abound, but several are associated with major
leaps in epidemiological progress: the germ theory,
competing theories of multi-causality, and epidemiological methodology itself. The following brief
treatise postulates an empirical generalization, and possible law of nature, which is not at all trivial.
The content for the following statement was originally stated as an axiom (and two corollaries) by
Stallones.4 However, an axiom is a fundamental assertion, undeniable by definition.5 Resting epidemiology
on an axiom is placing it akin to a religion, not a
science. Science must seek to ground itself by laws of
nature: laws that are falsifiable. With slight manipulation over the phraseology used by Stallones, one
comes not to an axiom but to a falsifiable universal
statement.
To communicate effectively, scientific law must be
able to be stated; such statement typically consists of a
range, a scope and a field.6 In our case the range is
disease, the scope is non-randomly distributed, and the
field is for humans. The empirical generalization is:
Modern science typically follows a process of
hypotheses generation and testing. Hypotheses may be
falsified or supported based on harvested empirical evidence. Such evidence typically speaks to the constructs
of; probability, time-order, strength of association, specificity, consistency, predictive performance, and coherence.3 For knowledge of our world to progress,
scientists must move from standing hypothesis (fact) to
theory. The importance of theory is evident if one is
only to recall the germ theory and consequent discoveries due to it. Theory (and law) is what ties the strands
of our world together, allowing scientific discovery to
make fantastic leaps of progress.
All disease is non-randomly distributed.
1.1
Adding the field and an empirical delimiter spatiotemporal constructs, gives us:
For humans, all disease is non-randomly distributed by
spatio-temporal constructs.
1.2
The base statement (1.1) alone stands as a universal
statement. It is worthy of note that spatio-temporal
constructs (1.2) include both risk factors (aetiologic)
and risk indicators (non-aetiologic), including time. 7
The question arises, is this universal statement a fact,
a nomic generalization, an empirical generalization, a
law-like statement, or a scientific law? Following
Kaplan's criteria set forth in The Conduct of Inquiry,6 one finds the statement is: (1) truly universal,
unrestricted by time and space, for the statement refers
to any disease at any time any where; (2) not vacuously
true, empirical evidence on specific diseases can be
used to attempt to provide falsifying evidence against
Karhausen declares that, save the trivial, there are no
universal statements or laws of nature in medicine and
epidemiology. I believe the author is in grave error by
this statement. Universal statements and laws of nature
Department of Epidemiology and Biosutisiics, College of Public
Health, University of South Florida, 13201 Bruce B Downs Boulevard,
Tampa, Florida 33612-3805, USA.
899
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
the statement; (3) possibly derivable from other laws;
and (4) true, as shown by the current collective knowledge. Since the statement has not yet been derived
from other law (criteria 3), it stands as an empirical
generalization.
Karhausen closes the paper with a call for '... an
analysis in depth of some of the philosophical issues
raised by our discipline.' Science is non-existent without theory. However, as the oxymoronic title of this
letter alludes, epidemiology is in dire need of theoretical growth. The above statement, a confirmed empirical generalization (and possible scientific law), is
the philosophical basis of epidemiological exploration.
Only with a clear understanding of such philosophical
underpinnings can epidemiology truly advance. For example, it took a widespread understanding and usage of
the germ theory before questions of multi-causality could
be addressed. The statement of empirical generalizations and scientific laws is far from trivial. For such
statement helps to ground the science of epidemiology.
Grounding is necessary, if for no other reasons than to
assist in the training of future generations of epidemiologists and to develop neoteric theory. These statements
(1.1 & 1.2), in various forms, have been adopted over
the past hundred years; thereby allowing epidemiology
to develop as a discipline and a science. By openly
stating its underlying philosophy, a science marks itself
for assault. The bastions of science are meant to be
assailed, for only by such method can we hope to attain
an enhanced picture of our world.
REFERENCES
1
Karhausen L R. The poverty of Popperian epidemiology, Int J
Epidemiol 1995, 24: 869-74.
Whitehead A N. Science and the Modern World. New York:
Macmillan Company, 1967.
3
Susser M. Epidemiology, Health, <t Society: Selected Papers.
New York: Oxford University Press, 1987.
"Stallones R A. To advance epidemiology. Ann Rev Public
Health 1980; 1: 69-82.
3
Babbie E. The Practice of Social Research. Belmont:
Wadsworth Publishing, 1992.
6
Kaplan A. The Conduct of Inquiry. San Francisco: Chandler
Publishing, 1964.
7
Meitenen O S. Theoretical Epidemiology. New York: John Wiley,
1985.
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