The Commens Dictionary
Quote from ‘Intention’
Second intentions are those which are formed by observing and comparing first intentions. Thus the concept “class” is formed by observing and comparing class-concepts and other objects. The special class-concept, ens, or what is, in the sense of including figments as well as realities, can only have originated in that way. Of relative second intentions, four are prominent–identity, otherness, co-existence, and incompossibility.