in philosophical history, an appellation given by Epicurus to his doctrine of logic. It was called canonica, as consisting of a few canons or rules for directing the understanding in the pursuit and knowledge of truth. Epicurus's canonica is represented as a very flight and insufficient logic by several of the ancients, who put a great value on his ethics and physics. Laertius even affirms us, that the Epicureans rejected logic as a superfluous science; and Plutarch complains that Epicurus made an unskillful and pernicious use of syllogisms. But these censures seem too severe. Epicurus was not averse to the study of logic, but even gave better rules in this art than those philosophers who aimed at no glory but that of logics. He only seems to have rejected the dialectics of the stoics, as full of vain subtleties and deceits, and fitted rather for parade and disputation than real use. The stress of Epicurus's canonica consists in his doctrine of the criteria of truth. All questions in philosophy are either concerning words or things; concerning things, Canonical. we seek their truth; concerning words, their signification: things are either natural or moral; and the former are either perceived by sense or by the understanding. Hence, according to Epicurus, arise three criterions of truth, viz. sense, anticipation or pronouncement, and passion. The great canon or principle of Epicurus's logic is, that the senses are never deceived; and therefore, that every sensation or perception of an appearance is true.