proposition

…step from one or more propositions, called premises, to a new proposition, usually called the conclusion. A rule of inference is said to be truth-preserving if the conclusion derived from the application of the rule is true whenever the premises are true. Inferences based on truth-preserving rules are called deductive,…

…which deal respectively with words, propositions, and syllogisms. These works, along with the Topics, the Sophistical Refutations, and a treatise on scientific method, the Posterior Analytics, were grouped together in a collection known as the Organon, or “tool” of thought.

…concerned with certain kinds of propositions that can be analyzed as consisting of (1) usually a quantifier (“every,” “some,” or the universal negative quantifier “no”), (2) a subject, (3) a copula, (4) perhaps a negation (“not”), (5) a predicate. Propositions analyzable in this way were later called categorical propositions

…logic, the abstract study of propositions, statements, or assertively used sentences and of deductive arguments. The discipline abstracts from the content of these elements the structures or logical forms that they embody. The logician customarily uses a symbolic notation to express such structures clearly and unambiguously and to enable manipulations…

True propositions can be divided into those—like “2 + 2 = 4”—that are true by logical necessity (necessary propositions), and those—like “France is a republic”—that are not (contingently true propositions). Similarly, false propositions can be divided into those—like “2 + 2 = 5”—that are false by…

Propositions may also be built up, not out of other propositions but out of elements that are not themselves propositions. The simplest kind to be considered here are propositions in which a certain object or individual (in a wide sense) is said to possess a…

…branch of logic is the propositional calculus, hereafter called PC, so named because it deals only with complete, unanalyzed propositions and certain combinations into which they enter. Various notations for PC are used in the literature. In that used here the symbols employed in PC first comprise variables (for which…

…words used to combine simpler propositions into more complex ones. In addition to the conditional, which had already been explored by the Megarians, they investigated disjunction (or) and conjunction (and), along with words such as since and because. Some of these they defined truth-functionally (i.e., solely in terms of the…

…A, E, I, and O propositions. The proposition “Every b is an a” is now written “Aba”; “Some b is an a” is written “Iba”; “No b is an a” is written “Eba”; and “Some b is not an a” is written “Oba.” Careful examination of the relations obtaining between…

Propositions such as “all triangles have three sides,” “all bachelors are unmarried,” and “all red things are coloured” are necessarily true in one or both of these senses. Likewise, it was held that propositions that are contingently true, or true merely by virtue of the…

…unpublished, was his generalization concerning propositions that in every true affirmative proposition, whether necessary or contingent, the predicate is contained in the notion of the subject. This notion seemed to imply determinism and thus to undermine human freedom—as did Leibniz’s conception of monads, the soul-like individual substances that make up…

…facts, those expressible by atomic propositions. More complex propositions, called molecular propositions, are built up out of atomic propositions via the logical connectives—such as “… or …,” “… and …,” and “… not …”—and the truth-value of the molecular proposition is in each case a function of the truth-values of…

…thoughts in this sense “propositions.”

…of which is that a proposition can express a fact by virtue of sharing with it a common structure or “logical form.” This logical form, however, precisely because it is what makes “picturing” possible, cannot itself be pictured. It follows both that logic is inexpressible and that there are—pace Frege…