 Hume claims that liberty, understood properly, is “essential to morality” (EHU 8.31). The above interpretations provide two different explanations for why this is the case. The standard approach says that Hume’s compatibilism is about the logic of our concepts and the justification of our judgments. Our judgments about responsibility entail judgments about the causal antecedents of action, and such judgments are consistent with determinism. On this view, the liberty of spontaneity is essential to morality because attributions of responsibility, which permeate morality (as well as law and religion), are unjust and unreasonable without it. According to the naturalist approach, liberty is essential for a different reason. The naturalist reading emphasizes that, on Hume’s view, attributions of responsibility are made via feelings of approval and disapproval, not judgments (T 2.3.2.6; Russell 1995: 60–4). They are, in his terminology, impressions or sentiments rather than ideas. These sentiments are partially caused by beliefs about the source of the behavior to which we are responding. We would not feel approval or disapproval unless we had been led to think of the person as the cause of the action. If we believed that her action was either compelled or uncaused, we would neither approve nor disapprove of her. Our responses or thoughts would be about something else. Hume’s claim, on the naturalist reading, is that in approving or disapproving of the agent—in feeling gratitude or resentment, for example—we hold her responsible, and in holding her responsible we believe that her conduct is free. Hume does not argue that the latter justifies attributions of responsibility. His claim is that it causally contributes to such attributions. They are made by means of feelings of approval and disapproval, which are a core feature of human morality as we know it. Therefore, the idea of liberty, properly reconciled with necessity, is essential to morality.