THREE TYPES OF FUNCTIONS: A PRELIMINARY DISTINCTION

Suppose that a magnificent chair was designed as a throne for the king; i.e., it was designed to seat the king. However, it is actually used by the king's guards to block a doorway in the palace.

In answering this question I suggest that all of this information would be relevant. It would be appropriate to say what the chair was designed to do, what it is used to do, and what it actually does which serves to benefit something. As this example indicates the answers to these questions need not be the same. Accordingly one might distinguish three types (some might want to say senses) of function: design functions, use functions, and service functions. The design function of that chair is to seat the king; its use function is to block the doorway; its service function is to attract visi­tors to the palace and thus induce more financial contributions.^{[101] [102]}

Before trying to clarify this distinction one additional aspect of func­tion statements should be noted, the possibility of relativization. An item can have a function for someone or within one system or set of activities that is not its function for another. In swimming (for the swimmer) the, or at least one, (use or service) function of the legs is to help keep the body horizontal in the water; in walking their function is to help keep the body vertical; in soccer it is to kick the ball.

In pointing to various possible relativizations I am not saying what some philosophers have said about function statements, namely, that they must always be understood as relativized to some “system” and time.^[103] To understand the claim that the function of that mousetrap is to catch mice one need not identify or be able to identify anyone for whom, or any system within which, or any occasion on which, this is its function. To be sure, this mousetrap may on a given occasion, or within some system, or for some particular person serve a function other than that of catching mice, and if so we may need to identify the occasion, and so forth. But we need not conclude from this that all function statements must be so rela­tivized. Indeed it is the (design) function of that mousetrap to catch mice whether or not it serves that function for anyone, or within any system, or on any occasion.

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