 While this doctrine has theological roots, it was also motivated by two features of human knowledge. The first has to do with those principles of thought that appear to be necessarily, not contingently, true. These include mathematical truths and principles such as that of non-contradiction or sufficient reason. While such principles are essential to thought, it is difficult to see how they could be derived from sense perception. (Aristotle had provided an empiricist account of the origin of mathematical ideas  [sect. 3.2],  but this was, and remains, contested.) A second motivation was related to the Aristotelian ideal of science. Scientia, as we have seen, involved a grasp of the essential properties of perceived objects. But this, too, involves a kind of insight that can seem to lie beyond the capacity of the senses  (sect. 3.2).  Advocates of divine illumination argued that these kinds of knowledge were possible only because the human mind has access to the mind of God. More precisely, it was possible only because God bathed the human mind in his own, uncreated light. This allowed it not only to grasp necessary truths, but to understand the essences of created beings by reference to their exemplars in the divine mind.