Abstract: According to Kant, a man’s action is an effect of some natural causes on the one hand, and an effect of an unique kind of intelligible cause on the other hand. Here natural cause and intelligible cause respectively correspond to man as an appearance and man as thing in itself (the subject in itself). Some commentators hold that this twofold cause conception of human action puts Kant into the so-called overdetermination dilemma. This critique of Kant is not acceptable, for intelligible cause and natural cause constitute a perfect causal chain: intelligible cause first of all causes decision and act of will as a kind of natural cause, and then decision and act of will causes action.