Law of identity
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In logic, the law of identity states that an object is the same as itself: A ≡ A. Any reflexive relation upholds the law of identity. When discussing equality, the fact that "A is A" is a tautology.
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[edit] History
Parmenides the Eleatic (circa BC. 490) formulated the principle Being is (eon emmenai) as the foundation of his philosophy. Aristotle, by contrast, took the Principle of contradiction as his first principle, and does not refer explicitly to the Law of Identity, although the law is often attributed to him (particularly by the proponents of Ayn Rand's writings). His only apparent reference to the principle is in Book VII of the Metaphysics:
Now "why a thing is itself" is a meaningless inquiry (for—to give meaning to the question 'why'—the fact or the existence of the thing must already be evident—e.g., that the moon is eclipsed—but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical, unless one were to answer, 'because each thing is inseparable from itself, and its being one just meant this.' This, however, is common to all things and is a short and easy way with the question.)
Both Thomas Aquinas (Met. IV., lect. 6) and Duns Scotus (Quaest. sup. Met. IV., Q. 3) follow Aristotle. Antonius Andreas, the Spanish disciple of Scotus (d. 1320) argues that the first place should belong to the principle 'Every Being is a Being' (Omne Ens est Ens, Qq. in Met. IV., Q. 4), but the late scholastic writer Francisco Suarez (Disp. Met. III., § 3) disagreed, also preferring to follow Aristotle.
Leibniz claimed that the principle of Identity, which he expresses as 'Everything is what it is,' is the first primitive truth of reason which is affirmative, and the Principle of contradiction, is the first negative truth (Nouv. Ess. IV., 2, § i), arguing that "the statement that a thing is what it is, is prior to the statement that it is not another thing" (Nouv. Ess. IV.. 7, § 9). Wilhelm Wundt credits Gottfried Leibniz with the symbolic formulation, "A is A."[1]
Locke (Essay Concerning Human Understanding IV. vii. iv. ("Of Maxims") says:
... whenever the mind with attention considers any proposition, so as to perceive the two ideas signified by the terms, and affirmed or denied one of the other to be the same or different; it is presently and infallibly certain of the truth of such a proposition; and this equally whether these propositions be in terms standing for more general ideas, or such as are less so: e.g. whether the general idea of Being be affirmed of itself, as in this proposition, "whatsoever is, is"; or a more particular idea be affirmed of itself, as "a man is a man"; or, "whatsoever is white is white" ...
J.S. Mill formulates the law as: "Whatever is true in one form of words, is true in every other form of words, which conveys the same meaning" (Exam. of Hamilton, p. 409).
African Spir proclaims the principle of identity (or law of identity A ≡ A) as the fundamental law of knowledge, which is opposed to the changing appearance of the empirical.[2]
[edit] Trivia
In 2002 Jonathon Keats held a petition drive to pass 'A = A' as statutory law in Berkeley, California. Specifically, the proposed law stated that, "every entity shall be identical to itself". Any entity caught being unidentical to itself was to be subject to a fine of up to one tenth of a cent. The law did not pass.[3]
[edit] See also
[edit] Allusions
[edit] People
- Keith Donnellan
- David Kaplan
- Saul Kripke
- Hilary Putnam
- Ayn Rand and Objectivism
- W.V. Quine
- John Searle
- African Spir
[edit] References
- ^ La philosophie éternelle ou traditionnelle, la métaphysique, la logique, la raison et l'intelligence
- ^ Forschung nach der Gewissheit in der Erkenntniss der Wirklichkeit, Leipzig, J.G. Findel, 1869 and Denken und Wirklichkeit: Versuch einer Erneuerung der kritischen Philosophie, Leipzig, J. G. Findel, 1873.
- ^ San Francisco Chronicle
- ^ [1]
- ^ [2]
