 But the implication of this idea for the definitions of hylomorphic compounds is obvious: since matter appears to be a part of such a compound, the definition of the compound will include, as a part, the definitions of its material components. And this consequence seems implausible to Aristotle. A circle, for example, seems to be composed of two semicircles (for it obviously may be divided into two semicircles), but the definition of circle cannot be composed of the definitions of its two semicircular parts. For, as Aristotle points out (1035b9), semicircle is defined in terms of circle, and not the other way around. His point is well taken, for if circles were defined in terms of semicircles, then presumably semicircles would be defined in terms of the quarter-circles of which they are composed, and so on, ad infinitum. The resulting infinite regress would make it impossible to define circle at all, for one would never reach the ultimate “simple” parts of which such a definition would be composed.