ردهها philosopher Ludwig Wittgenstein (1889 – 1951) Participations: گسترشها Tractatus Logico-Philosophicus Tractatus Logico-Philosophicus 1921 author Ludwig Wittgenstein On Certainty On Certainty 1960 author Ludwig Wittgenstein Blue Book Blue Book 1933 author Ludwig Wittgenstein Philosophical Investigations Philosophische Untersuchungen 1953 author Ludwig Wittgenstein