Teleology [addendum]
Teleological explanations are said to be forward looking. We ask why Lauren is walking and are told her purpose, which is to buy ice cream when she gets to the shop. Or we ask why vertebrates have kidneys and are told their function, which is filtering blood. In both cases, the end explains the means; something at a time is explained by something else at a later time. This inverts the usual order of causal explanations: If Johnny's throwing the ball explains the window breaking, his throwing preceded the breaking.
Purposive Explanations
How does Lauren's purpose explain her walking? Many philosophers would now say that the relation between her purpose and her walking is a special instance of ordinary physical causation. On a standard version of physicalism, an agent's purpose consists of beliefs and desires, which involve brain states that represent what is believed and desired. If Lauren is walking to the shop to buy ice cream, she has both a desire to buy ice cream and a belief that walking to the shop will let her do so. It is not her buying ice cream but her intention to do so that causes her walking, and since her intention precedes her walking, the usual explanatory order is preserved.
Some physicalists question the causal power and explanatory relevance of beliefs and desires. For example, Jaegwon Kim (1998) argues that, given that mental properties cannot be strictly identified with basic physical properties (a thesis of functionalism), they are causally redundant, since basic physical properties suffice to cause behavior. And Jerry Fodor (1991) argues that, given that the contents of beliefs and desires depend on the relations of an agent to his or her environment (the thesis of content externalism), contents do not explain behavior, since an agent's behavior is caused by his or her intrinsic properties. Similar doubts can be raised with regard to the causal power and explanatory relevance of functions. However, by no means is everyone persuaded by these arguments, and their conclusions are anyway consistent with (what Sydney Shoemaker calls) the core realizers of beliefs and desires being the causes of behavior.
Functional Explanations
When functions are attributed to artifacts and components of organic systems, we seem to use a teleological notion of what something is for. "The switch has the function of turning on the light" seems equivalent to "The switch is for turning on the light" (that is why it is there). "Pineal glands have the function of secreting melatonin" seems equivalent to "Pineal glands are for secreting melatonin" (that is why they are there). Not all locutions involving the word function have this teleological flavor. "X performs the function of Z-ing" does not entail "X has the function of Z-ing" or "X is there in order to Z." So only function ascriptions of the latter kind are relevant here.
Artifact functions depend on the purposes of the people who design, make, or use the artifacts: The switch has the function of turning on the light because someone put it there (or later adapted it) for that purpose. Organic function ascriptions in biology seemed more puzzling once the bearers of the functions were no longer seen as God's artifacts.
However, many philosophers of biology now believe that natural selection can replace God in function ascriptions. A popular view, developed and defended by, among others, Larry Wright (1976), Ruth Millikan (1989), Karen Neander (1991a, 1991b), and Peter Schwartz (2002), is that the biological function of a trait is what that type of trait was selected for. According to this etiological theory of function, the pineal gland has the function of secreting melatonin because that is what pineal glands did that caused them to be preserved and/or proliferated in the population. This gives functional explanations of the teleological variety a parallel form to purposive explanations: They both explicitly refer to an effect of the item being explained, but in doing so they implicitly refer to a past event to explain it (intentional selection for the effect, or natural selection for the effect). Numerous objections to the etiological theory have been made, but while it has not gone entirely unscathed, in the view of most philosophers of biology it remains the theory to beat (although see, e.g., Christopher Boorse [2002], who strongly disagrees).
As with purposes, an important issue is the explanatory role of functions. According to Wright (1976), a trait's function explains why it is there. Robert Cummins (1975) argues against this, that functions explain how systems operate. An overall capacity of a complex system is explained by a functional analysis, which describes the contributing capacities of the parts of the system, and the contributing capacities of each of their parts, in turn. According to Cummins, a function of a component part is its contribution to a capacity under analysis.
A problem with Cummin's account is that it does not account for the normativity of function ascriptions. Function ascriptions are normative (although not prescriptive) in the sense that they permit the possibility of malfunction: For example, my pineal gland could have the function to secrete melatonin and at the same time it could lack the capacity to secrete melatonin because it is malfunctioning. His account also leaves a lot to be determined by the interests of the researcher. Which overall capacity is to be analyzed and in which environment its exercise is to be analyzed is settled by the interests of the researcher. Thus the account is not naturalistic (it makes use of intentional terms). It is also inaccurate. For example, those interested in explaining death by cancer can give a functional analysis of the kind that Cummins describes. But contributions to death by cancer are not normal (proper) functions by virtue of their role in producing death by cancer. These problems suggest that the analysis is at best incomplete as it stands.
While Cummins's (1975) analysis of functions is problematic, he is right about the importance of functional analysis. This has led some to suggest that biology employs two notions of function, with distinct explanatory roles: a teleological notion for teleological explanations and a notion of a contributing capacity for functional analysis. However, this cannot be the right way to understand their respective explanatory roles if the etiological analysis is the correct analysis of functional norms, since physiological biology, which provides functional analyses of living systems, makes important use of the distinction between normal and abnormal functioning in doing so. Neander (1991b) suggests that the teleological/etiological notion of a function permits an idealized functional analysis, the idea being that we describe the functional organization of a normal system (as opposed to the malfunctioning of an abnormal system) by describing the capacities for which each of its parts was selected.
Bibliography
Boorse, Christopher. "A Rebuttal on Functions." In Functions: New Essays in the Philosophy of Psychology and Biology, edited by André Ariew, Robert Cummins, and Mark Perlman. New York: Oxford University Press, 2002.
Cummins, Robert. "Functional Analysis." Journal of Philosophy 72 (1975): 741–765.
Fodor, Jerry. "A Modal Argument for Narrow Content." Journal of Philosophy 88 (1991): 5–26.
Kim, Jaegwon. Mind in a Physical World. Cambridge, MA: MIT Press, 1998.
Millikan, Ruth. "In Defense of Proper Functions." Philosophy of Science 56 (1989): 288–303.
Neander, Karen. "Functions as Selected Effects." Philosophy of Science 58 (1991a): 168–184.
Neander, Karen. "The Teleological Notion of Function." Australasian Journal of Philosophy 69 (1991b): 454–468.
Schwartz, Peter. "The Continuing Usefulness Account of Proper Function." In Functions: New Essays in the Philosophy of Psychology and Biology, edited by André Ariew, Robert Cummins, and Mark Perlman. New York: Oxford University Press, 2002.
Wright, Larry. Teleological Explanation. Berkeley: University of California Press, 1976.
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