He dismissed the possibility of a private language using his beetle-in-a-box thought experiment in Philosophical Investigations, and wrote a work which concludes that "what we cannot speak of we must pass over in silence."
In one work, this philosopher discusses the meaning of the word "slab" as told by a builder to his assistant.  G.E. Moore provided the material for the "two hands" argument used in this philosopher's On Certainty. He argued that the inability to feel someone else's pain has to do with grammar, not metaphysics, in The Blue and Brown Books. He dismissed the possibility of a private language using his beetle-in-a-box thought experiment in Philosophical Investigations, and wrote a work which concludes that "what we cannot speak of we must pass over in silence." For 10 points, name this author of Tractatus Logico-Philosophicus.
In one work, this philosopher discusses the meaning of the word "slab" as told by a builder to his assistant.  
Ludwig Wittgenstein