Wittgenstein, Russell, and Our Concept of the Natural Numbers 

Saul Aaron Kripke was an American analytic philosopher and logician. He was Distinguished Professor of Philosophy at the Graduate Center of the City University of New York and emeritus professor at Princeton University. Kripke is considered one of the most important philosophers of the latter half of the 20th century.
Wittgenstein Rules and Private Language
by Saul Kripke
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