Aristotelian logic or the traditional study of deduction deals with four socalled categorical or subjectpredicate propositions which can be defined by S a P ⇔ All S is P universal affirmative or A proposition S i P ⇔ Some S is P particular affirmative or I proposition S e P ⇔ No S is P universal negative or E proposition S o P ⇔ Some S is not P particular negative or O proposition S is called a subject or minor term and P is called a predicate or major term of a proposition We could think of S and P as oneplace predicates or sets The bilateral diagram is a way to understand relations among categorical propositions It is a square divided into four smaller square cells SP SP SP SP A red counter or 1 within a cell means that there is at least one thing in it A gray counter or 0 within a cell means there is nothing in it So we may not put both counters in the same cell A red counter in the cell SP means Some S is P; a gray counter in the cell SP means No S is P The red counter in the upper rectangle means that there is at least one S symbolically ExS ⇔ S i S But if we put the counter on the common line of squares SP and SP we dont know whether the proposition S i P is true 1 or false 0 so it has value unknown or undetermined ½ The same holds for S o P Analogously the value of the proposition S a P is ½ unless we put the gray counter in the square SP S a P 1 or in SP S a P 0