Ludwig Wittgenstein (1889–1951), Austrian philosopher. Tractatus Logico-Philosophicus, sct. 7 (1922).
Wittgenstein had elaborated in the book's Preface: "What can be said at all can be said clearly, and what we cannot talk about we must pass over in silence." Karl Popper, in his Conjectures and Refutations (1963) reported Franz Urbach's rejoinder to this: "But it is only here that speaking becomes worthwhile."