De Morgan's Laws (Logic)/Conjunction/Definition
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Theorem
De Morgan's Law for Conjunction can be used as a definition for the logical operator that is conjunction:
- $p \land q := \neg \left({\neg p \lor \neg q}\right)$
Historical Note
This definition appears in the introductory material of 1910: Alfred North Whitehead and Bertrand Russell: Principia Mathematica: Volume $\text { 1 }$, and some other authors follow their lead.
Sources
- 1910: Alfred North Whitehead and Bertrand Russell: Principia Mathematica: Volume $\text { 1 }$ ... (previous) ... (next): Chapter $\text{I}$: Preliminary Explanations of Ideas and Notations