Editing Law of identity (section)

===Modern philosophy===
[[Gottfried Wilhelm Leibniz]] claimed that the law of identity, which he expresses as "Everything is what it is", is the first primitive truth of reason which is affirmative, and the law of noncontradiction 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."<ref>{{cite journal |last1=Curley |first1=E. M. |date=October 1971 |title=Did Leibniz State "Leibniz's Law"? |journal=The Philosophical Review |volume=8 |issue=4 |pages=497–501}}</ref> [[Identity of indiscernibles|Leibniz's Law]] is a similar principle, that if two objects have all the same properties, they are in fact one and the same: Fx and Fy if x = y.

[[John Locke]] (''[[Essay Concerning Human Understanding]]'' IV. vii. iv. ("Of Maxims") says:

{{quote|[...] 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" [...]}}

[[Afrikan Spir]] proclaims the law of identity as the fundamental law of knowledge, which is opposed to the changing appearance of the empirical reality.<ref>''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.</ref>

[[George Boole]], in the introduction to his treatise ''[[The Laws of Thought]]'' made the following observation with respect to the nature of language and those principles that must inhere naturally within them, if they are to be intelligible:

{{quote|There exist, indeed, certain general principles founded in the very nature of language, by which the use of symbols, which are but the elements of scientific language, is determined. To a certain extent these elements are arbitrary. Their interpretation is purely conventional: we are permitted to employ them in whatever sense we please. But this permission is limited by two indispensable conditions, first, that from the sense once conventionally established we never, in the same process of reasoning, depart; secondly, that the laws by which the process is conducted be founded exclusively upon the above fixed sense or meaning of the symbols employed.|}}

[[Objectivism]], the philosophy founded by novelist [[Ayn Rand]], is grounded in three axioms, one of which is the law of identity, "A is A." In the Objectivism of Ayn Rand, the law of identity is used with the concept existence to deduce that that which exists is something.<ref>{{Cite book |last=Rand |first=Ayn |url=http://worldcat.org/oclc/969408226 |title=For the New Intellectual |oclc=969408226}}</ref> In Objectivist epistemology logic is based on the law of identity.<ref>{{Citation |title=UNIFORM ABBREVIATIONS OF WORKS BY AYN RAND |url=http://dx.doi.org/10.2307/j.ctt9qh7ww.18 |work=Concepts and Their Role in Knowledge |pages=269–270 |publisher=University of Pittsburgh Press |doi=10.2307/j.ctt9qh7ww.18 |access-date=2021-09-01|url-access=subscription }}.</ref>