 In his review of the Philosophical Investigations, he summarised the book in a very effective way, drawing particular attention to Wittgenstein’s critique of a family of “realist” or “essentialist” theories of meaning according to which the meaning of a word is the object designated or referred to by that word. Feyerabend argued that Wittgenstein was attempting a reductio ad absurdum of realist theories, showing that they had the untenable implication that we could not be said to know the meaning of words which we nevertheless constantly use in totally unproblematic ways.