ARGUMENT, a word meaning "proof," "evidence." (Lat. arguere, to make clear, from a root meaning bright, appearing in Greek apyrls, white). From its primary sense are derived such applications of the word as a chain of reasoning, a fact or reason given to support a proposition, a discussion of the evidence or reasons for or against some theory. "Argument" means a synopsis of the contents of a book, the outline of a novel, play, etc. In logic it is used for the middle term in a syllogism, and for many species of fallacies (see FALLACY). In mathematics (q.v.) the term has received special meanings; in mathematical tables the "argu ment" is the quantity upon which the other quantities in the table are made to depend. The term is also used in astronomy (q.v.).