have observed, such a specification results in an entity's being individuated by occasions in which it takes part in the
activity: American Airlines may have carried three millionpassengersbut only one milliondifferentpeople, thanks to lots
of frequentflyers.
Returning to purposes, consider a word likemail. What makes somethingmailrather than a piece of paper is (in part)
that it is intended to be sent and delivered; for instance being burnable is not an essentialpart of being mail. But let us
be a bit more specific about“intended to be sent and delivered.”Sometimes it happens that a pieceof mail is notsent,
or, more commonly, alas, that it is not delivered. So these activities do not constitute necessary conditions for
something to be mail. On the other hand, they are too important to the understanding of the concept of mail to be
described as mere“tendencies”or“probabilistic associated activity.”I believe the correct characterization is to be
found in Ruth Millikan's notion of“proper function.”Roughly,“having a proper function is a matter of having been
‘designed to’or of being‘supposed to’(impersonal) perform a certain function”(Millikan 1984: 17). An object need
notactuallyever perform its proper function. Millikan's striking exampleis a sperm, only oneof millions of whichever
performs its proper function of fertilizing an egg. This can hardly be described as a“tendency”or a“probabilistically
associated activity.”This modality for proper functions—the possibility that the activity never takes place but is yet
essential—is also just what we need for the cases ofembryoandfiancéediscussed above.
What kinds of things can have proper functions? There are two major classes. Thefirst isartifacts:objects constructed
by volitional beings who have some function in mind for the objects, or who benefit fro mtheir functioning. As
Millikan is quick to point out, we want to include here not just concrete artifacts such as pencils and beaver dams but
also abstract artifacts such as myths and contracts. Millikan is particularly concerned with claiming that beliefs have a
proper function, namelytoguide reasoning and action.Shecanthen say thatfalse beliefsstillhavea proper function; it
is just that, like undelivered mail, they fail to fulfill it.
A second importantclass ofobjects with proper functionsisparts. Inthecaseofparts ofartifactssuch as theback ofa
chair, the proper functionis clear: it serves as a part of the proper functionof the artifact. But in addition the parts of
organisms have one or more proper functions: the heart is to pump blood, the kidney is to remove wastes from the
blood, the leaves of a plant are to perfor mphotosynthesis, and so forth.
A possiblevariantonproperfunctionisoccupation, whichisincomplementarydistributionwithproperfunction:only
humans (and perhaps animals like sheepdogs, bloodhounds, and packhorses) have occupations; only artifacts and