 Presumably these thinkers object to lines and continuity being parts of the definitions of circle and triangle on the grounds that they are matter, comparing them to other sorts of matter that are obviously inadmissible in definitions. Aristotle criticizes this line of thought, which suggests that maybe he does think that certain sorts of matter or at least matter-like concepts are admissible in definitions. However, the fact that he groups flesh and bones with bronze and stone as the sort of matter that is obviously inadmissible suggests that he does not think that they are parts of the form of man.