Character Analysis
Hume doesn't fight it out with individual philosophers. His focus is on philosophers in general, though he draws a line between ancient and modern thinkers.
He argues that modern philosophers have been way too vague and abstract when discussing morality. That's why he's gone for the empirical method—he wants to focus on real-world experiences. Another thing he criticizes them for is being caught up in theology. These guys don't explore morality with an open mind but bring everything back to their religious views. Hume's like, "change the record already!"
Hume has a higher opinion of the ancient moralists, whom he sees as "the best models" (IV.11). Still, he observes that even their theories can sometimes be muddled: they claim that virtue is based on reason, yet, in reality, seem to view morals as stemming from sentiment. It's a good job Hume's around to get to the bottom of this.