Although the metaphysics of light is fundamentally non-Aristotelian in nature, Grosseteste clearly was concerned to use it to explain many of the features of the Aristotelian cosmos—the system of nested spheres, the distinction between the movement of celestial and sublunary bodies, and so forth. In like manner, in his commentary on the Physics he interprets fundamental ideas in Aristotle’s natural philosophy in terms of the light metaphysics, explaining Aristotle’s theory of potentiality in terms of the replicability of form and holding that every bodily species comes to be by “the greater or lesser replication of the simple first bodily form,” light (Dales 1963a, 17).  Likewise, Aristotle’s three principles: form, privation and the underlying subject, are interpreted as the first form light, the impurity of light in things, and first matter respectively. In On Bodily Movement and Light, Grosseteste identifies nature, conceived by Aristotle as an internal source of movement and rest, with the first form, light, and claims that all kinds of bodily change are the “multiplicative force” of the first bodily form, light (Baur 1912, 92).