Any classification of games, no matter how determined and what principle of division is chosen, reveals an irreducible category: games of chance. This does not mean that this category is destitute of ambiguity. Because, after all, is it sufficient for chance to play a part in such recreational activity and thus transform it into a game of chance? We can investigate the nature of chance, the part it must play and the extent of its role. It is rather clear that in many games one can discern an element of chance, without this being enough to define these games as games of chance. The chess-player who develops a system of attack cannot take into account all the possibilities of his antagonist's reply. He is naturally inclined to speculate on a partially fortuitous future and to rely on a certain amount of “good luck: “ si fortuna iuvat. We have chosen a rather paradoxical example, since in such competition the best calculator is theoretically sure of winning or of stalemating. But in all human occupations, and therefore a fortiori in recreational activities, the indetermination of the future plays a role which can be lessened but not reduced to nothing. From this point of view, what game is not a game of “chance?” Without what sport commentators call “the glorious uncertainty of sport” which is simply the global name for a vertiginous number of unforeseeable factors, determined beyond doubt, but indeterminable in their totality, and so foreign one to another that they cannot be “integrated,” a match of rugby or tennis would have no spectacular interest. It would be the equivalent of an experimental verification.