The Law of Noncontradiction

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		+	Metaphysically, this law asserts:: "Nothing can be both A and not-A." For propositions: "A proposition, P, can not be both true and false."
		+	The Law of Noncontradiction is defended through [[Rertortion|retortion]]: any attempt to contradict the concept must rely on the acceptance that contradictions are false.
-		+	It can be proven using [[Propositional Logic]]:
-	The Law of Noncontradiction can be proven using [[Propositional Logic]]:	+
	Proof (by reductio):		Proof (by reductio):
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	QED		QED
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		+	The Law of Noncontradiction, while appearing prima facie and necessarily true, is questioned by modern logicians. See [[Paraconsistent Logic]] and [[Dialetheism]].
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		+	==References==
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		+	* Copi, I. M, Cohen, C., (2001), "Introduction to Logic", 11th Edition.

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Revision as of 23:25, 18 June 2007

Metaphysically, this law asserts:: "Nothing can be both A and not-A." For propositions: "A proposition, P, can not be both true and false."

The Law of Noncontradiction is defended through retortion: any attempt to contradict the concept must rely on the acceptance that contradictions are false.

It can be proven using Propositional Logic:

Proof (by reductio):

1) (A & ~A) [Proposition] 2) A [Conjunction elimination from 1] 3) ~A [Conjunction elimination from 1] 4) ~(A & ~A) [Reductio, 1 - 3]

QED

The Law of Noncontradiction, while appearing prima facie and necessarily true, is questioned by modern logicians. See Paraconsistent Logic and Dialetheism.

References

• Copi, I. M, Cohen, C., (2001), "Introduction to Logic", 11th Edition.