compatibilism, Thesis that free will, in the sense required for moral responsibility, is consistent with universal causal determinism. It is important to distinguish the question of the logical consistency of belief in universal causal determinism with belief in free will from the question whether the thesis of free will (or that of causal determinism) is true. Compatibilists need not assert (though many have) the reality both of free will and of causal determinism. Among incompatibilists, some maintain the existence of free will and accordingly deny universal causal determinism, while others uphold universal causal determinism and deny the existence of free will.