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Contrary ( contrariety ; from French contraire "opposite") are two terms , judgments or statements that are mutually exclusive in logic . The opposite is contradiction .


Contradiction exists when, in a series of coordinated terms, judgments or statements, these are the furthest apart and show the greatest possible differences. By not setting one contrary term, the setting of the other is not conditioned, e.g. B. something “green and red”: what is red cannot be green, but what is not red does not necessarily have to be green. Two contrary judgments about an object cannot be true at the same time. But both can be wrong.

Contrary to Aristotle

For Aristotle, contrariness is a kind of difference ( Greek  διαφορά , diaphora ). In the case of contrariness, he advocated a genre common to both members. He distinguished between opposing members with a common genus ( black and white with the genus color ), members with opposing genres ( justice with the genus virtue , injustice with the genus vice ) and members that are themselves genres ( good and bad ).


For example, “ black ” and “ white ” are mutually exclusive, but what they have in common is the generic term “ color ”. Concepts, judgments or statements that denote the greatest possible contrast, but still allow a third judgment as possible, are contrary. It is a so-called polar-contrary contrast, in which the terms represent the (relative) endpoints of a graduated scale.

In classical logic, a sub-contrarian opposition is the logical opposition between statements that cannot both be false, but can be true at the same time, the falsehood of one therefore implies the truth of the other. For example, some birds are migratory birds, but some species of birds are not migratory birds.

Individual evidence

  1. Paul Thormeÿer, Philosophical Dictionary , 1922, p 106
  2. Aristotle, Categories , 6, 6 a15-18
  3. Aristotle, Categories , 11, 14 a23-25
  4. Max Apel / Peter Ludz, Philosophical Dictionary , 1958, p. 164
  5. Kuno Lorenz, contrast , in: Jürgen Mittelstraß (ed.), Enzyklopädie Philosophie und Wissenschaftstheorie, Volume 3, 2008, p. 41
  6. ^ Niko Strobach, Introduction to Logic , 2005, p. 62
  7. Elena Tatievskaya, propositional logic , 2003, p. 72