In the Preface to Ethics V, Spinoza returns to his preoccupation with what is wrong with Descartes’s treatment of the human mind, focusing more directly now on the way it construes the role of reason in the management of emotion. He offers a scathing critique of Descartes’s view of the mind as having absolute power over its passions through the exercise of a supposedly free human will. He cannot wonder enough, he says, that a philosopher of Descartes’s apparent calibre should have made the preposterous claim that minds and bodies – such utterly different and distinct kinds of thing – should nonetheless causally interact.

Spinoza’s own focus remains firmly on the human mind’s embodiment within the necessities governing the totality of things. He promises that his alternative remedy for the passions will present the power of a mind as defined only by understanding, with no role for a specious free will. Once again, Spinoza puts a strong emphasis on the dynamics of the human mind’s vacillations, and the steadying effects of reason. If affects can be separated from thoughts of an external cause, then – by his earlier arguments – ‘the Love, or Hate, toward the external cause is destroyed, as are the vacillations of mind arising from these affects’ (EVP2).