Philosophy of Biology

REDUCTIONISM IN BIOLOGY

Alex Rosenberg

Physicalism about biology is the thesis that all facts, including all the non-
macromolecular biological facts, are fixed by the facts of molecular biology. Re-
ductions argue that physicalism mandates that non-molecular biological explana-
tions need to be completed, corrected, made more precise or otherwise deepened
by more fundamental explanations in molecular biology. Antireductionism does
not dispute physicalism’s metaphysical claim about the fixing of biological facts by
macromolecular ones, but denies it has implications either for explanatory strate-
gies or methodological morals. The antireductionists holds that explanations in
functional biology need not be corrected, completed or otherwise made more ade-
quate by explanations in terms of molecular biology.

1 POST-POSITIVIST INTERTHEORETICAL REDUCTION

Reduction was supposed by the post-Logical Empiricists to be a relation between
theories. In Ernest Nagel’sStructure of Science[1961], reduction is characterized
by the deductive derivation of the laws of the reduced theory from the laws of the
reducing theory. The deductive derivation requires that the concepts, categories
and explanatory properties, or natural kinds of the reduced theory be captured in
the reducing theory. To do so, terms that figure in both theories must share com-
mon meanings. Though often stated explicitly, this second requirement is actually
redundant as valid deductive derivation presupposes univocality of the language
in which the theories are expressed. However, as exponents of reduction noted,
the most difficult and creative part of a reduction is establishing these connections
of meaning, i.e. formulating “bridge principles”, “bi-lateral reduction sentences”,
“coordinating definitions” that link the concepts of the two theories. Thus it was
worth stating the second requirement explicitly. Indeed, early and vigorous op-
ponents of reduction as the pattern of scientific change and theoretical progress
argued that the key concepts of successive theories are in fact incommensurable in
meaning, as we shall see immediately below.
Within a few years Watson and Crick’s Nobel for uncovering the structure and
function of DNA, reductionists began to apply their analysis to the putative re-
duction of Mendelian or population genetics to molecular genetics. The difficulties
they encountered in pressing Watson and Crick’s discovery into the mold of the-
oretical reduction became a sort of “poster-child” for antireductionists. In an
early and insightful contribution to the discussion of reduction in genetics Ken-
neth Schaffner observed that reduced theories are usually less accurate and less

General editors: Dov M. Gabbay,
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Handbook of the Philosophy of Science. Philosophy of Biology

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