ABSTRACT
The main thesis of this study can be stated in one short sentence: Bodies of psychological knowledge are social institutions. Or, in a slightly longer formulation: Both scientificpsychological theories and folk-psychological bodies of knowledge have the same form of existence as do marriage, money, or the monarchy. They are social; they are conventional; and they are theories and bodies of knowledge only because they are taken to be theories and bodies of knowledge. Why are some pieces of metal coins-that is, money? Because there are collectives that take these pieces of metal to be coins. Why are some sets of sentences theories about the mind? Because there are collectives that take these sets of sentences to be theories about the mind.
