It is often supposed that if an action is the end of a causal chain, i.e. determined, and the causes stretch back in time to events for which an agent has no conceivable responsibility, then the agent is not responsible for the action. The dilemma adds that if an action is not the end of such a chain, then either it or one of its causes occurs at random, in that no antecedent events brought it about, and in that case nobody is responsible for its occurrence either. So whether or not determinism is true, responsibility is shown to be illusory. See also free will, libertarianism (metaphysical).