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5Ludwig Wittgenstein. Tratatus Logico - Philosophicus. D Pears and B McGuinnes(trans. ). London: Routledge and Kegan Paul, 1961. "Preface" ,4. 003.
6Ludwig Wittgenstein. Philosophical Investigations. R Rhees and G E M Anscombe ( eds. ), G E M Anscombe (trans.) (revised edition. ). New York: MacMillan, 1958 (1953). § 111.