In this paper I consider the context and significance of the first instalment of Hume's A Treatise of Human Nature , Books One and Two, on the understanding and on the passions, published in 1739 without Book Three. I argue that Books One and Two taken together should be read as addressing the question of the relation between reason and passion, and place Hume's discussion in the context of a large early modern philosophical literature on the topic. Hume's goal is (...) to show that the passions do not require government by reason, and to illustrate various ways in which the passions of social beings regulate themselves. The underlying theme of the first Treatise is thus a new theory of sociability: sympathetic sociability. (shrink)