Centre de Recherche, Centre Hospitalier Côtes-des-Neiges, Montréal, Canada.

A human brain after many years of life can be compared with a chessboard (of gigantic complexity) on which the layout of the pieces reflects the history and identity of one particular game. Normal interpersonal communication, as in education, can be likened to the making of moves that respect the rules of chess, and so preserve the continuity and identity of the game. By contrast, physical brain manipulation can be compared with the removal or addition or displacement of chessmen without regard to the rules. The end result might or might not be a legitimately playable game; but, in a sense that could be important, the play would not in general be a continuation of the same game.