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Leibniz 's Principle Of The Identity Of Indiscernibles

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Leibniz’s Principle of the Identity of Indiscernibles A1: Leibniz’s Principle of the Identity of Indiscernibles (PII) The Principle of the Identity of Indiscernibles (PII) claims that in nature, there cannot be two individual things that differ in number alone (Primary Truths, p. 32). The symbolic notation of (PII)—∀P (Pa Pb) —> ( a = b)—indicates that if, for every property P, thing a has property P if and only if thing b has property P, then thing a is identical to thing b. Hence, if two things (a and b) have exactly the same properties, they must be identical—i.e. they must be the same thing (numerically one). For example, Billy offers a complete description of all the properties that constitute Sacramento, and Bob offers a complete …show more content…

31-32). So, in this paper, identities will be called unqualified (or basic) primary truths, and definitions will be called qualified (or derivative) primary truths. A3: Retracing Leibniz’s Reasoning P1: Unqualified Primary Truths are identities. Sub-P1: P1 is supplemented by the Principle of Contradiction (PC). P2: Qualified Primary Truths are partial identities with the help of a priori definitions. Sub-P2: P2 is supplemented by the Principle of Sufficient Reason (PSR). C: So, there cannot be two indiscernible Primary Truths that differ in number alone (PII). Unqualified primary truths are identities since they (i) assert themselves (e.g., ‘A is A’) or (ii) deny the opposite of their opposites (e.g., ‘A is not not A’). Examples of Unqualified primary truths are: (i) ‘I am always identical to myself’, and (ii) ’I am always not not identical to myself’. Leibniz claims that these type truths can be supplemented by his Principle of Contradiction (PC). PC states that anything which implies a contradiction is false. Hence, if people disagree with the claim (i) ‘I am always identical to myself’ they would be claiming a falsehood. I can immediately point out that they are stating a contradiction—i.e. ‘A is not A’ contradicts ‘A is A’. Qualified primary truths are partial identities since they are identities if and only if they have a priori definitions that are independent of

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