All truths can be formulated as judgments, and all judgments can be formulated as propositions. While judgments are made up of ideas, however, propositions are made up of terms.

An idea is an act of representation by the mind in which a specific object is represented. Every idea is a representation, and ideas are signified by terms. So everything that's true for a term is true for the idea it signifies. But as a term can express only one part of an idea, it isn't always the case that what's true for an idea is true for the term that signifies it.

Terms are general when they express a general idea and particular in the opposite case.

General terms have two characteristics – comprehension, which refers to the collection of characteristics that distinguishes the signified idea from all others, and extension or scope, the collection of things covered by the term.

Extension and comprehension follow this law: “Extension varies inversely with comprehension.”

This means that if many characteristics distinguish the term from all others, the number of things it will cover will be small. Conversely, if the term covers many things, it must be because it has fewer distinctive characteristics.

The upper limit of comprehension is infinity, and the lower limit of extension is unity. When an idea is infinitely comprehensive, it has an infinite number of characteristics and could apply to only one single thing. There couldn't be two distinct objects that share an infinite number of characteristics.