Hume's Dissertation on the Passions stands to Book 2 of his Treatise as the first and second Enquiries stand to Books 1 and 3 respectively. However, while the two Enquiries are evidently substantial reworkings of their Treatise ancestors, containing much that is different and new, the Dissertation appears to consist merely of superficially adapted excerpts from Treatise Book 2. I argue that this first impression is mistaken, by showing how Hume's view of the indirect passions is modified in the later work. In the Treatise, he views them as simple impressions; in the Dissertation, they are complex perceptions, part impression and part idea. I argue, furthermore, that Hume's account of the origin of the indirect passions only works on this later view, and suggest that this is why he changed his mind. The Dissertation, I conclude, is an improvement on its Treatise forerunner, and not merely a précis of it.