Lives and Opinions of Eminent Philosophers

​A proposition differs from a question, an inquiry, a command, an oath, a curse, an assumption, an address, and a quasi-proposition. For a proposition is that which in speaking we declare, which is either true or false. A question is a complete matter, like the proposition, but demanding an answer, for example: "Is it day?" And this is neither true nor false, so that "It is day" is a proposition, but "Is it day?" is a question. An inquiry is a matter to which it is not possible to respond symbolically with "Yes," as in the case of a question, but one must say: "He lives in this place."

​A command is a matter which in speaking we command, for example: "Go thou to the streams of Inachus." An oath is a matter... An address is a matter which, if one were to speak it, one would address someone, for example: "Most glorious son of Atreus, king of men, Agamemnon." A quasi-proposition is that which, having a propositional utterance, falls outside the genus of propositions on account of the excess or affective tone of some particle, for example: "Fair indeed is the maiden's chamber!" "How like the sons of Priam is the herdsman!"

​There is also a matter of doubt, differing from a proposition, which, if one were to speak it, one would be in perplexity: "Is sorrow somehow kindred to life?" Questions, inquiries, and things similar to these are neither true nor false, whereas propositions are either true or false. Of propositions, some are simple, and others not simple, as Chrysippus, Archedemus, Athenodorus, Antipater, and Crinis say. Simple, then, are those composed of a proposition that is not duplicated, for example: "It is day." Not simple are those composed of a duplicated proposition or of distinct propositions:

​of a duplicated proposition, for example: "If it is day, it is day;" and of distinct propositions, for example: "If it is day, there is light." Among simple propositions are the negative, the denier, the privative, the predicative, the definite, and the indefinite; and among propositions not simple are the conditional, the pseudo-conditional, the conjunctive, the disjunctive, the causal, and the one declaring the more and the less.... And a negative is, for example: "Not: it is day." A species of this is the super-negative. A super-negative is the negative of a negative, for example: "Not: it is not day;" and it establishes: "It is day."

​A denier is that composed of a negative particle and a predicate, for example: "No one walks." A privative is that composed of a privative particle and a proposition in potentiality, for example: "Inhumane is this man." A predicative is that composed of a nominative case and a predicate, for example: "Dion walks." A definite proposition is that composed of a deictic nominative case and a predicate, for example: "This one walks." An indefinite proposition is that composed of an indefinite particle or particles and a predicate, for example: "Someone walks," "That one moves."

​Of propositions not simple, a conditional is, as Chrysippus says in his Dialectics and Diogenes in his Art of Dialectic, that which is formed by means of the connective conjunction "if." And this conjunction promises that the second follows from the first, for example: "If it is day, there is light." A pseudo-conditional is, as Crinis says in his Art of Dialectic, a proposition sub-connected by the conjunction "since," beginning from a proposition and ending in a proposition, for example: "Since it is day, there is light." And this conjunction promises both that the second follows from the first and that the first subsists.