Biology Reference
In-Depth Information
recognized that the point of metabolism was to convert the energy of foodstuffs
into a chemical substance which could then provide energy to other vital pro-
cesses. The phenomenon was then reconstituted in a very different way.
The second feature of mechanistic explanation to emphasize is that the com-
ponent parts and operations of a mechanism are within the mechanism and can
only be identified by taking the mechanism apart, either literally or conceptu-
ally.
7
There is a compositional relation between parts of a mechanism and the
mechanism itself, and so it is useful to characterize the parts as at a lower level
than the mechanism itself.
8
Appealing to parts and their operations is reduction-
istic, in a sense familiar to scientists, although not necessarily to philosophers.
9
But it is important to be clear on what the appeal to parts and their operations is
designed to do - it explains what resources a given mechanism has that enable
it to behave in a particular way when in the context in which it functions. It
does not, in any way, supplant the need to identify the manner in which the
mechanism as a whole operates under various conditions in its environment.
Moreover, and especially important for the purposes of the current paper, it does
not mitigate the importance of considerations of how the parts are organized for
explaining what the mechanism does or indeed for understanding how a part of
the mechanism is operating. It is an important feature of mechanistic explanation
to recognize that parts will operate differently under different conditions,
10
and
that the organization in which they are incorporated is often a major factor in
determining these conditions and hence the operation performed by the part.
7
Although literal decomposition has often been a productive strategy in biological research for identifying the
operation associated with a component (e.g., isolating an enzyme through fractionation), it can also disrupt
the operation when it is dependent on coordinated interactions with other components. A clear example is
that the rate at which an enzyme catalyzes a given reaction is dependent on the concentrations of substrates,
products, and effectors. Often the effects of being embedded in a particular organization are only realized after
noting the differences in behavior in the original system and the isolated component and determining the role
of the organized setting in determining the operation of the component. Hence, in the end, decomposition is
often conceptual rather than literal - in a model the theorist specifies an operation performed by the part and
how that performance relates to other operations occurring within the mechanism.
8
Although this conception of levels is compositional in the sense articulated by Wimsatt (1976), the levels
that result are only defined locally within the mechanism. Moreover, there is no requirement that the parts
which interact with each other are of remotely the same size dimensions - in one mechanism membranes may
interact with whole bacterial cells whereas in another they may interact with ions. Accordingly, the conception
of reduction that emerges is local because the levels to which a scientist appeals are only identified in the
context of the attempt to explain a given phenomenon. Moreover, typically a given investigation goes one or
two levels down. There is no goal of reducing all sciences to some most fundamental one (Bechtel, 2006).
9
In particular, this sense of reduction does not focus on theories and logical relations between them, as in
classical philosophical accounts of theory reduction (Nagel, 1961). For discussion, see Bechtel and Hamilton
(in press).
10
Boogerd et al. (2005) emphasize the fact that parts behave differently under different conditions and invoke
it as part of their case for the claim that biological systems exhibit emergent properties. Under their analysis,
a property is emergent if it cannot be predicted from what is known by studying the part in isolation or in the
context of simpler systems.
