Biological Function

One of the central concepts in the more medical parts of biology, particularly physiology, is the concept of function. It is impossible to understand the way we classify organ systems without this concept. The function of the heart is to pump blood. Hence any blood pump is a heart—even if there are some structural differences between the hearts of different species or (as mechanical hearts demonstrate) differences in the material makeup of the heart. So, what makes something a heart is fundamentally its function or purpose. This poses a philosophical problem, because the concept of function is a teleological notion. The function of the heart is to pump blood is simply another way of saying that the heart is designed to pump blood. But, who is the designer? Prior to Darwin the answer would have been an appeal to God.

Philosophers have attempted to account for the apparent goal-directed nature of biological science in two different ways. One solution is to accept that functions are goal directed, but to appeal to natural selection. Rather than a conscious designer, natural selection designed the heart to pump blood. The etiological view of functions (sometimes called Wright functions) gives an explanation of why a function is there in historical terms. More precisely, "The function of X is Z means (a) X is there because it does Z and (b) Z is a consequence (or result) of X's being there" (Wright, p. 139-168). To Larry Wright, "a heart beats because its beating pumps blood" (p. 40).

In contrast, in 1975 Robert Cummins rejected the goal-directed, historical approach to functions. What matters in thinking of functions is the contribution it makes to a whole system, the role that it plays in bringing about the performance of that system.

Early-twenty-first-century commentators have concluded that each approach captures a different notion of function. Where Larry Wright attempts to account for why a function is there (a function as opposed to an accident), Cummins explains what a function does, what it is good for (whether it is an accident or not). Continued debate over whether an etiological account can be developed in the Wright mode and how to overcome various problems continues (Cummins and Perlman).

The concept of function plays an especially important role in medicine since health and disease are often understood as normal (species typical) functioning or dysfunction respectively.

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