(1) The Interrogative Sentence;
(2) The Imperative Sentence;
(3) The Exclamatory Sentence;
(4) The Enunciative Sentence; Indicative Potential.
It is with the last of these only that logic is concerned.
§ 176. The proposition, therefore, corresponds to the Indicative and Potential, or Conditional, sentences of grammar. For it must be borne in mind that logic recognises no difference between a statement of fact and a supposition. 'It may rain to-morrow' is as much a proposition as 'It is raining now.'
§ 177. Leaving the grammatical aspect of the proposition, we must now consider it from the purely logical point of view.
§ 178. A proposition is a judgement expressed in words; and a judgement is a direct comparison between two concepts.
§ 179. The same thing may be expressed more briefly by saying that a proposition is a direct comparison between two terms.
§ 180. We say 'direct comparison,' because the syllogism also may be described as a comparison between two terms: but in the syllogism the two terms are compared indirectly, or by means of a third term.