 As crucial bits of our psychology, the emotions are also important to epistemology. Here, though, the position of many early modern philosophers has often been misunderstood, especially when it is assumed that they oppose reason to the emotions, to the detriment of the latter. (We might call this the ‘Mr. Spock’ gloss on early modern philosophy.) It is true that many philosophers held that the emotions can sometimes lead our reasoning astray, and they offer various epistemic techniques to minimize this cognitive interference. Malebranche, for instance, imbedded his account of the passions in the reforming project of The Search After Truth (1674–5), and many accounts of method, e.g., Arnauld’s and Nicole’s Logic, or the Art of Thinking (1662), or Part II of Mary Astell’s Serious Proposal to the Ladies (1697), included an account of the emotions as an indispensable part of their epistemic techniques. But none of these accounts assumed that the emotions are inevitably disruptive to our reason, however important it may be to temper them. Descartes particularly emphasized the functionality of our passions, first for practical, but also for theoretical reasoning, and suggested that proper discipline should allow us to maximize the epistemic value of the emotions. Malebranche and Spinoza were less sanguine about our chances of doing so, but even Malebranche maintained that the passions are functional in several respects. Hobbes, on the other hand, mounted a number of contrasts between passions and the “common measure” of reason. But these seem somewhat at odds with his claims about the operation of the passions in driving mental activity. Here it is worth considering Spinoza’s account of the relation between reason and the affects, for it offers a kind of gloss on Hobbes. It is, Spinoza maintained, only our passive emotions that can produce conflict with the dictates of our reason; our active affects accord well with reason. Hume, of course, denied that it makes any sense to speak of a conflict between reason and passion, when he declared that reason not only is, “but ought only to be” the slave to the passions – a dictum that seems to apply to theoretical as well as practical reason. Later eighteenth-century philosophers developed the view that our reasoning faculties, and particularly our language, are a historical development from our emotions; this seems to have been the view of Condillac and Rousseau.