The diversity of types of stone tools, as of any other class of artifacts, may be regarded as due to differences in the nature and functional relations of the relevant variables existing in the given situations in which these artifacts were produced. These relevant variables may be conceived as of three major kinds: those associated primarily with the individuality of the given artisan, those arising primarily from the cultural matrix in which the artisan lived and worked, and those directly or indirectly due to the resources and nature of the physical environment in which the artisan and his culture existed. In setting up such categories, a corresponding functional dissociation must not be assumed. Each recognizable element in each category is of course functionally related to every other. But the archae6logist must, in attempting to evaluate his material, schematize in some such fashion. He must evaluate, as well as he can, each of the variables involved.