ABSTRACT
The difference between affirmative and negative propositions is not one of fundamental importance, but rather one of convenience. Such propositions are called categorical propositions. The following may serve as examples of such propositions: The earth is a planet, The earth is not flat, All planets move in elliptical orbits, No planets are fixed, Some stars are self-luminous, and Some planets are not self-luminous. The examples of categorical propositions will have shown that they vary not only in the way in which the predicate is asserted of the subject, but also as regards the extent of the subject of which the predicate is asserted. The forms of propositions may be studied to a considerable extent apart from their actual terms, and terms may be studied to some extent apart from the propositional forms in which they occur.
