Editing Term logic (section)

== Basics ==
The fundamental assumption behind the theory is that the [[formal system|formal]] model of [[propositions]] are composed of two [[Symbol (formal)|logical symbol]]s called terms – hence the name "two-term theory" or "term logic" – and that the [[reasoning]] process is in turn built from propositions:
*The ''term'' is a [[part of speech]] representing something, but which is not true or false in its own right, such as "man" or "mortal". As originally conceived, all terms would be drawn from one of ten ''[[Categories (Aristotle)|categories]]'' enumerated by Aristotle in his ''[[Organon]]'', classifying all objects and qualities within the domain of logical discourse.
*The [[formal system|formal]] model of ''proposition'' consists of two terms, one of which, the "[[predicate (grammar)|predicate]]", is "affirmed" or "denied" of the other, the "[[subject (grammar)|subject]]", and which is capable of [[truth]] or [[falsity]].
*The ''[[syllogism]]'' is an [[inference]] in which one [[proposition]] (the "[[Consequent|conclusion]]") follows of necessity from two other propositions (the "[[premise]]s").

A proposition may be universal or particular, and it may be affirmative or negative. Traditionally, the four kinds of propositions are:
:* A-type: Universal and affirmative ("All philosophers are mortal")
:* E-type: Universal and negative ("All philosophers are not mortal")
:* I-type: Particular and affirmative ("Some philosophers are mortal")
:* O-type: Particular and negative ("Some philosophers are not mortal")
This was called the ''fourfold scheme'' of propositions (see [[Syllogism#Types|types of syllogism]] for an explanation of the letters A, I, E, and O in the traditional square). Aristotle's ''original'' [[square of opposition]], however, does not lack [[Syllogism#Existential import|existential import]].