In the Nicomachean Ethics, Aristotle famously says that virtue is a hexis. This term, which comes down to us from the Latin habitus, is often transliterated in English as “habit,” though some commentators note that Aristotle is claiming that virtue is something active requiring attention, practice, and reflection, whereas the word “habit” suggests something passive and involuntary. Descartes’ use of the term habitus, or habitude in French, is more complex. He sometimes uses it to refer to our natural dispositions or to ones that we formed in childhood prior to being in full possession of our reason. Typically, these are vicious habits that Descartes encourages us to overcome by replacing them with virtuous ones, but unlike the former the latter must be actively cultivated. Habits play a prominent role in two aspects of Descartes’ philosophy: his account of happiness and virtue on the one hand and his epistemology on the other. What follows is a separate discussion of each.

1.Virtue and Habits

Although Descartes often treats habits as obstacles to the search after truth, habits are instrumental and essential to living a virtuous and happy life. Descartes’ treatment of habits within his moral psychology and philosophy is developed most fully in his final work, Passions of the Soul (1649). There, Descartes explains that humans are a union or composite of mind and body, and passions are modes of this union (see human being). Passions and actions that promote the preservation of the union are virtuous and good, and those that harm the union are bad. Because humans cannot directly arouse or suppress passions or directly will the body to move, they must do so indirectly by means of representing things that are joined to certain passions (Passions I.45). The joining of particular ideas to particular passions results from habit – a disposition to act in a certain way that is acquired by nature or by repetition. Thus, habit formation is a key ingredient in the training and guiding of our actions. In the pursuit of happiness, habits serve as the mechanism for regulating our passions – instituting the right idea-passion couplings (by nature or repeated experience) that produce beneficial actions.