Collier's New Encyclopedia (1921)/Logic

LOGIC, as known in the present day, is a development and modification of the techné dialektikē = art of reasoning, which Aristotle, utilizing the labors of his predecessors, and notably those of Zeno of Elea, molded into something like consistent shape. The first development of Aristotelian logic was by the Scholastics. At the time of the Reformation, probably as a protest, Scholasticism was depreciated, and at some of the Scotch universities it was discarded for Ramism. The subtle distinctions and keen disputations of the Schoolmen led in the next century to Bacon's condemnation of the perversion &mdash; not of the cultivation &mdash; of logical pursuits. Locke was not so moderate, as may be seen in his &ldquo;Essay.&rdquo;

Generally speaking, down to the first half of the 19th century there was little dispute as to how logic should be defined. The Port Royalists had certainly called it the Art of Thinking; but the Art or Science of Reasoning, or the Art and Science of Reasoning met with little opposition as a definition. This is how Whately defines it, and a writer of such opposite opinions as Tongiorgi, S. J., has substantially the same words; and a parallel passage to Whately's explanation as to how logic is at once a science and an art, occurs in Liberatore, who is read in many of the ecclesiastical colleges in Rome.

Deductive logic, syllogistic logic; in which no more is inferred in the conclusion than is implicitly contained in the premises.

Equational logic, a system of logical notation in which propositions are expressed in the form of equations.

Inductive logic, the science which treats of inductive reasoning, by which, broadly speaking, a general proposition is inferred from a number of particular propositions.

Modified logic, that logic which is concerned in the investigation of truth and its contradictory opposite error; of the causes of error, and the impediments to truth and their removal, and of the subsidiaries by which human thought may be strengthened and guided in its functions.