The Enlightenment encouraged widespread speculation into the nature of the 'human' in order to determine the vital element in the constitution of the modern citizen. This process began in earnest in the seventeenth century as an elaboration of the function of the 'person', the semi-fictional creature who acts as the atom of the body of the state in Thomas Hobbes's political philosophy, and as the representative of identity in that of John Locke. Fiction is used to rinse away the indefinite residue of sense impressions that might obscure the sufficient nature of the thinking thing: the mind or soul, endowed with free will and immune to all accidents. Daniel Heller-Roazen's comments on the Metaphysics of Morals, shows how Kant makes the person the embodiment of those very qualities of humanity that its invention was supposed to attain, elevating the means of historical development into its end.