Lŏg'ic, n.

(lōj'ĭk), n. [Fr. logique, Pr., It., Sp., & Pg., logica, Lat. logica, logice, Gr. λογική, (sc. τέχνη), fr. λογικός, belonging to speaking or reason; λόγος, speech, reason; λέγειν, to say, speak.] The science of pure and formal thought, or of the laws according to which the process of pure thinking should be conducted; the science of the formation and application of general notions; the science of classification, judgment, reasoning, and systematic arrangement.

Logic is the science of the laws of thought, as thought; that is, of the necessary conditions to which thought, considered in itself, is subject. Sir W. Hamilton.

Logic is distinguished as pure and applied. “Pure logic is a science of the form, or of the formal laws, of thinking, and not of the matter. Applied logic teaches the application of the forms of thinking to those objects about which men do think.” Dr. W. Thomson.