In a recent paper Norman Malcolm has argued that mechanism is an inconceivable position.' By this Malcolm does not mean that mechanism is logically contradictory. Rather mechanism is a position which cannot be asserted or argued for. For, according to Malcolm, asserting a position and arguing for a position involve purposeful behavior and mechanism excludes all purposeful behavior. Thus mechanism may well be true, but ifit is true, then it cannot be asserted or argued for. The bulk of Malcolm's paper is an attempt to develop the thesis that mechanism excludes all purposeful behavior. This exclusion turns on another of Malcolm's theses, namely that a neurophysiological explanation and a purposeful explanation of the same bodily movements are impossible. If this latter thesis is shown to be false, Malcolm's argument for the inconceivability of mechanism collapses. Malcolm is quite aware of this and in his final paragraph he says: