Abstract

In a 1994 paper entitled "Ist eine reine Inhaltslogik moglich?" M. Liske attempted to show that Leibniz's theory of intensional concepts suffers from a serious inadequacy. Liske begins by defining the intension of a concept in two slightly different ways. Broadly conceived, Int is the set of all concepts B which are contained in A, while in a narrow sense, Int* consists of all such B other than A itself. These definitions entail that the tautological concept 0 has an empty intension in the narrow sense, i. e. Int*= Ø, while Int={0}. Furthermore it follows that the intension* of a negated individual-concept also is empty. And from this Liske concludes that the intensions* of all negative concepts must be empty. This, however, is a fallacy which rests upon conflating the empty set, Ø, with the non-empty set {Ø}, which contains Ø as its only element.