The study of the principles of reasoning.

Logic (or dialectic) was one of the arts in the medieval trivium.

Over the course of the 20th century, notes A.D. Irvine, "the study of logic has benefited, not only from advances in traditional fields such as philosophy and mathematics, but also from advances in other fields as diverse as computer science and economics" (Philosophy of Science, Logic and Mathematics in the Twentieth Century, 2003)

See also:


From the Greek, "reason"


  • "But of all the arts the first and most general is logic, next grammar, and finally rhetoric, since there can be much use of reason without speech, but no use of speech without reason. We gave the second place to grammar because correct speech can be unadorned; but it can hardly be adorned before it is correct."
    (John Milton, The Art of Logic, 1672)
  • "Logic is the armory of reason, furnished with all defensive and offensive weapons. There are syllogisms, long swords; enthymemes, short daggers; dilemmas, two-edged swords that cut on both sides; sorites, chain-shot."
    (Thomas Fuller, "The General Artist," 1661)
  • Logic and Rhetoric
    "A good deal of everyday talk, even gossip, is intended to influence the beliefs and actions of others and thus constitutes a kind of argument. . . . [A]dvertisements often just provide product information rather than advance explicit arguments, yet clearly every such ad has an implied conclusion--that you should buy the advertised product.

    "Nevertheless, it is important to understand the difference between rhetoric that is primarily expository and discourse that is basically argumentative. An argument makes the claim, explicit or implicit, that one of its statements follows from some of its other statements. It at least implies that acceptance of its conclusion is justified if one accepts its premises. A passage that is purely expository gives us no reason to accept any 'facts' it may contain (other than the implied authority of the writer or speaker, as, for example, when a friend tells us that she had a good time at the beach)."
    (Howard Kahane and Nancy Cavender, Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life, 10th ed. Thomson Wadsworth, 2006)
  • Formal Logic and Informal Logic
    "Some logicians study only formal logic; that is, they work only with abstract models that have purely logical substance and content. . . .

    "Relating the abstract systems of formal logic to 'real' statements and arguments is not part of formal logic itself; it requires the consideration of many issues and factors beyond the basic logical forms of the statements and arguments. The study of the factors other than logical form relevant to the analysis and evaluation of statements and arguments of the kind that occur in everyday situations is known as informal logic. This study includes considerations of such things as: identification and clarification of vague or ambiguous statements; identification of unstated assumptions, presuppositions or biases and making them explicit; recognition of frequently used but highly questionable premises; and assessment of the strength of analogies between more or less similar cases."
    (Robert Baum, Logic, 4th edition, Harcourt Brace, 1996)

    Pronunciation: LOJ-ik