 Descartes’ abiding interest in medicine is prominent here, since the treatment of physical illness is an effective way of removing one of main sources of mental disturbance. Yet he is well aware of the limits of medical knowledge, and so he acknowledges that the passions also must be confronted directly: “They are domestic enemies with whom we are forced to keep company, and we have to be perpetually on guard lest they injure us” (AT IV 218/CSMK 249). Descartes prescribes to Elisabeth a two-part remedy for protecting herself against the harmful effects of the passions: “so far as possible to distract our imagination and senses from them, and when obliged by prudence to consider them, to do so with our intellect alone” (ibid.). The first part of the remedy relies on our ability to direct the imagination away from the immediate objects of the passions. Given this power, Descartes argues, “there might be a person who had countless genuine reasons for distress but who took such pains to direct his imagination that he never thought of them except when compelled by some practical nececessity, and who spent the rest of his time in the consideration of objects which could furnish contentment and joy” (AT IV 219/CSMK 250). Descartes speculates that this kind of cognitive therapy by itself might be sufficient to restore the patient to health. In circumventing the causal pathway by which the passion arises, the body will be returned to a healthy state. Descartes offers his own history as an example of this phenomenon: “From [my mother] I inherited a dry cough and a pale colour which stayed with me until I was more than twenty, so that all the doctors who saw me up to that time gave it as their verdict that I would die young. But I have always had an inclination to look at things from the most favorable angle and to make my principal happiness depend upon myself alone, and I believe that this inclination caused the indisposition, which was almost part of my nature, gradually to disappear completely” (AT IV 221/CSMK 251). This line of thought leads directly to the Passions of the Soul, in which Descartes discusses at length the causation and function of the passions.