Abstract
The function or intended use of a device such as a fire escape is escape from fire,
whether or not it is ever actually used as such or it acquires other uses.
Biological function, on the other hand, depends, in one way or another, on actual
use. Philosophical attempts to explain artifact function by analogy with
biological function or to build a unified theory of function are nonetheless
common. What such attempts routinely overlook, however, is the role of
forethought in intentional function. I defend the traditional intended use view of
function, emphasize the role of forethought and argue that design intentions are
rationally grounded in a design brief, for which there is no obvious natural
analogue.