"In the strident world of seventeenth-century philosophy, the mind-body problem was not a word puzzle that could be safely relegated to undergraduate classes. For men such as Descartes, Malebranche, and Leibniz, solving the mind-body problem was vital to preserving the theological and political order inherited from the Middle Ages and, more generally, to protecting human self-esteem in the face of an increasingly truculent universe. For Spinoza, it was a means of destroying that same order and discovering a new foundation for human worth."