There is significant confusion and disagreement, especially among specialists, about René Descartes's views on freedom. Employing careful translations of his writings, and keen attention to their philosophical and historical context, Libra: Descartes and Free Will offers a fresh interpretation of Descartes' views on freedom that dispels many of these common misunderstandings. Placing Descartes's views on free will within the Platonic tradition, Thomas M. Lennon argues that Descartes is a compatibilist who believed that the will's freedom is compatible with its choice being determined by perceived evidence for it one way rather than the other. To know the good is to do the good, and to know the true is to accept the true. Knowing the good but doing something else, knowing the true but accepting something else is impossible. Each of these would be a pragmatic contradiction. Another impossibility for Descartes is an unfree will, because what Descartes means by freedom of choice is simply the will itself.

Freedom in this Platonic tradition is to be able to act and accept with the intellect unimpaired by the distracting obstacles posed particularly by the senses. Exploring this conception of freedom, Libra delves into the fundamental philosophical issues of responsibility, error, certainty, and judgment in their historical and intellectual contexts.