 The first half of the twentieth century was an era of increasing rigour and professionalism in logic, and to most logicians of that period the use of games in logic would probably have seemed frivolous. The intuitionist L. E. J. Brouwer expressed this attitude when he accused his opponents of causing mathematics ‘to degenerate into a game’ (as David Hilbert quoted him in 1927, cited in van Heijenoort 1967). Hermann Weyl (cited in Mancosu 1998) used the notion of games to explain Hilbert’s metamathematics: mathematical proofs proceed like plays of a meaningless game, but we can stand outside the game and ask meaningful questions about it. Wittgenstein’s language games provoked little response from the logicians. But in the second half of the century the centre of gravity of logical research moved from foundations to techniques, and from about 1960 games were used more and more often in logical papers.