The humanist idealism Diderot and his contemporaries inherited attributed to the mind the regal privilege of making visible the rational order of things. Tirelessly constructing elaborate systems, Cartesian science and philosophy sought to comprehend nature by representing it as an object of vision. The work of reason and the act of revelation thus were not incompatible, since the Cartesian mind viewed matter as passive and inert, as bearing the unchanging imprint of an eternal, divinely created order that the mind could demonstrate and thus reflect. Enlightenment philosophy and science increasingly questioned such an ideal order, as well as the preeminent place accorded to the Cartesian notion of mind. Seeking to grasp an active, dynamic nature, the Enlightenment discourse of knowledge formulated other manners of presenting the relation between the human subject and the material world.

This experimentation occurs already in Diderot's earliest writings on nature. In the Encyclopédie article “Animal” for instance, he proposes that nature is essentially continuous, distinctions between animate and inanimate, animal and human, marking only a different degree of natural organization. The Lettre sur les aveugles also presents the human subject as part of one great whole and possessing no guarantee of a preestablished order to things grounded on some divine entity or transcendental principle.