The aim of this paper is to show that if and only if agents are motivated to act by good reasons for acting, they flourish, since, in so doing, they consciously act in accordance with their nature through virtuous actions. I offer an account of what good reasons for acting consist of reconsidering Aquinas’ natural inclinations. Based on a critical analysis of Anjum and Mumford’s work on dispositions in analytic metaphysics, I argue, contra Hume’s law, that Aquinas’ natural inclinations show that metaphysics is foundational for ethics. I claim that agents flourish as human beings if and only if they consciously act in accordance with natural inclinations. Natural inclinations naturally tend towards goods that depend on the metaphysical structure of human nature, by virtue of which agents have some powers that they should actualise in order to flourish. Intellect and will are the rational powers that distinguish human beings from other living beings. The will naturally desires what is good. If the will, through the input of the intellect, desires what is genuinely good for human beings according to their nature, it also directs the other powers to their own actualisation. Natural inclinations do not strictly necessitate agents to act in accordance with them, because, by virtue of their rational powers, agents should also recognise that they have a reason for acting in accordance with them. Thus, I will suggest that we can best appreciate the importance of natural inclinations from the first-person perspective.