Are definitions true or false?

Abstract

When a proposition which is true or false, necessary or contingent, consists of a definition (definiens) and a definiendum, its parts (the definiendum and the definition or defining part) are not, therefore, necessarily true or false. For if they were, then in ‘Man is a rational animal’, ‘man’ as definiendum and ‘a rational animal’ as definition (definiens) would have to be true or false. Now according to Ockham:

“It should be noted that when, significatively taken, a definition is predicated of something, the corresponding definitum, significatively taken, is also predicated of that thing and vice versa. Further, a proposition composed of a definition and a definitum that is hypothetical, possible, or the equivalent of either of these is a necessary proposition. The following, for example, are both necessary: ‘If man is, rational animal is’ (and vice versa; and ‘Every man can be a rational animal’ (where the subject stands for what can be). Nevertheless, no such affirmative proposition which is merely de iness? or depresent? is ever necessary. Thus, the simple propositions ‘Man is a rational animal’ and ‘Man is a substance composed of body and intellective soul’ are not necessary. The reason is that if there were no men, the propositions would be false.”¹