 With his philosophy of lights, he manages, nonetheless, to reconfigure some elements of physics. For instance, immaterial entities and material bodies are composed of varying degrees of intensity of light. The physical world is composed of dusky substances with dark accidents, while self-subsistent magnitude appears to replace prime matter which, like a number of traditional physical notions, becomes a mere mental concept that has no reality outside the mind. It is no longer the perception of the form of objects, but their constitutive lights that becomes the true object of knowledge (Walbridge 2000, 22–3). 