 The criterion for non-identity is stronger than the common one for real distinction: two things can be qualified as non-identical iff they belong to distinct categories. On the other side, the definition of difference does not exclude the possibility that two things which differ from each other share one or more properties (or forms). Thus, there are degrees of distinction, and what is more, the degree of distinction between two things can be read as the inverse measure of their (partial) identity. For instance, if we compare the list of the forms (both substantial and accidental) which constitute Socrates and those which make up the universal-man, it is evident that Socrates and the universal-man differ from each other, since there are forms which directly inhere in Socrates and not in the universal-man and vice versa; but it is also evident that the two lists are identical for a long section, that is, that Socrates and the universal-man, considered from the point of view of their metaphysical composition, are partially the same. As a result, the copula of the propositions which Penbygull deals with cannot be extensionally interpreted, as it does not mean that a given object is a member of a certain set, nor that a given set is included in another, but it always means degrees in identity between two compound entities.