Freedom is the least discussed thesis of Descartes' works. Two major issues are: (i) the Fourth Meditation is seen as an unfounded theodicy, an interlude, an interruption to the analytic order; (ii)some passages in Descartes' other works are seen as inconsistent with the Fourth Meditation. First, I argue that Descartes' treatment is philosophical, that freedom underlies his entire philosophical project, defending the indispensability of the Fourth to his metaphysics.I demonstrate that Descartes' conception of freedom differs from the mainstream conceptions, in (...) particular it admits of degrees of higher or lower quality or worth. The latter is connected with indifference, error and sin. The former with spontaneity, truth and goodness. I argue that autonomy and spontaneity are a sine qua non of freedom of highest grade. Secondly, I offer a solution to two problematic passages: Principles I 37, and the notorious letter to Mesland, drawing on Descartes' conception of freedom as the greatest good, on the internal relation between reason and freedom, and demonstrating that there is no inconsistency. Descartes' treatment and indispensability of freedom gives his conception a certain sublimity, and his conception of man a certain serenity: an autonomous rational human being irreducibly and substantially real. (shrink)