Philosophical Investigations is a work by the philosopher Ludwig Wittgenstein, published posthumously in 1953. Philosophical Investigations is divided into two parts, consisting of what Wittgenstein calls, in the preface, Bemerkungen, translated by G. E. M. Anscombe as "remarks". A survey among American university and college teachers ranked the Investigations as the most important book of 20th-century philosophy. (Wikipedia, CC BY-SA 4.0)