We are in the midst of a second Humean revolution. In his Treatise of Human Nature (1739-40), the Scottish philosopher David Hume argued that: ‘Reason is, and ought only to be the slave of the passions …’ By ‘passions’, Hume meant what we now call emotions. What gave him such faith in the passions that he could accept reason’s enslavement to them? Hume understood reason to be incapable of producing any action, and the passions to be the source of our motivations. So he insisted that we must attend to the passions if we want to understand how anything gets done. Much recent neuroscience has found that human rationality is weaker than is commonly presumed, and the emotions make it possible to make decisions by granting certain objects salience. Why does this second Humean revolution matter and what, if anything, can the second revolution learn from the first?