Biology Reference
In-Depth Information
Finally, we turn briefly to the issue of what we call 'realism'. Sufficiency
of a proposed mechanism does not insure that the proposed mechanism is the
one responsible for a given behavior. Even at the time that Jacob and Monod
received the Nobel prize for their discovery of the
lac
operon, the evidence
for it was indirect. There was good evidence that it was involved in the key
phenomena (biphasic growth and lactose consumption), but the actual mechanism
for repression had not been identified. Gilbert and Müller-Hill actually isolated
the repressor in 1966, subsequently showing that the repressor binds directly to
the DNA. Experimentally, it is interesting and difficult because the repressors
only are present in very low concentrations. This is one of many avenues we
will not follow out here.
4. MECHANISM AND EMERGENCE
The picture we have offered of mechanistic explanation is not inherently a
narrowly reductionist picture, at least if we construe reduction in terms of theory
reduction. It is, though, mechanistic in something like the sense advanced by
Machamer, Darden, & Craver (2000); in Stuart Kaufmann's (1970) apt terms, it
is an 'articulation of parts explanation'. It is an explanation of systemic behavior
in terms of the behaviors of constituent parts within the systemic context.
This last qualification is not idle. A fully reductive explanation would explain
systemic behavior in terms of the behaviors of constituent parts, where the
range of behaviors is motivated in terms appropriate to the lower level. The
constraints on a reductive explanation are substantial, provided it is intended to
demonstrate the sufficiency of lower level models for explanatory purposes. It
is not enough for a fully reductive explanation that we be able to redescribe
some behavior, or some mechanism, in terms of constituents, or even that we
can describe some state of the constituents sufficient for the behavior. This is
something we can, in principle, do in any case. To lay claim to a reduction of
one theory to another, it is necessary as well that we be able, at least, to show
that a sufficient mechanism can be constructed relying only on the explanatory
tools available within the lower level theory. This will sometimes require that
we include information concerning the relevance of organization and concerning
the behavior of constituents, neither of which are necessarily a function of
constitution alone. These can be understood as twin constraints on the adequacy
of reductionist models. Let us consider each briefly.
A description of a sufficient mechanism will often include information con-
cerning organization and not simply constitution. In rare cases, simple constitu-
tion is sufficient, and organization does not matter or is not crucial. Organization
will not matter when systemic behavior is an aggregative effect of constituent
behaviors and will matter less insofar as systemic behavior is an aggregative
