ABSTRACT
Syllogistic logic is concerned with the logical relations, especially the relations of inference, which hold between schemata of the kind we have just explained. There are three main branches of the traditional doctrine about these relations: 1. The Square of Opposition. 2. The Scheme of Immediate Inferences. 3. The Theory of the Syllogism. An inference is called a syllogism if it has the form of a syllogistic mood; and a syllogistic mood can be defined as an inferential schema in which (a) there are two premisses and one conclusion, each of which is an A, E, I or O schema; (b) premisses and conclusion together contain exactly three term variables, all unnegated; and (c) each term variable occurs in exactly two of the three schemata.
