That is better and more valuable which requires fewer, other circumstances being equal, just as that demonstration is better, other circumstances bei… - Robert Grosseteste

The first corporeal form, which some call corporeity, I hold to be light. For light of its own nature diffuses itself in all directions, so that from a point of light a sphere of light of any size may be instantly generated, provided an opaque body does not get in the way. Corporeity is what necessarily follows the extension of matter in three dimensions, since each of these, that is corporeity and matter, is a substance simple in itself and lacking all dimensions. But simple form in itself and in dimension lacking matter and dimension, it was impossible for it to become extended in every direction except by multiplying itself and suddenly diffusing itself in every direction and in its diffusion extending matter; since it is not possible for form to do without matter because it is not separable, nor can matter itself be purged of form. And, in fact, it is light, I suggest, of which this operation is part of the nature, namely, to multiply itself and instantaneously diffuse itself in every direction. Therefore, whatever it is that produces this operation is either light itself or something that produces this operation in so far as it participates in light, which produces it by its own nature. Corporeity is therefore either this light, or is what produces the operation in question and produces dimensions in matter in so far as it participates in this light itself and acts by virtue of this same light. But for the first form to produce dimensions in matter by virtue of a subsequent form is impossible. Therefore light is not the form succeeding this corporeity, but is this corporeity itself.

The head is borne towards the heavens and has two lights, as it were the sun and moon.

One cause, in so far as it is one, is productive of only one effect. I do not rule out several efficient causes of which one is nearer and another more remote in the same order. Thus when I say simply 'animal', I do not exclude another substance or particular substance. Hence motion, in so far as it is one, is productive of only one effect. But motion is present in every body from an intrinsic principle which is called natural. Therefore an efficient cause simply proportional to the motion is present in all bodies. But nothing is present in common in every body except primitive matter and primitive form and magnitude, which necessarily follows from these two, and whatever is entailed by magnitude as such, as position and shape. But simply through magnitude a body does not receive motion, as is clear enough when Aristotle shows that everything that moves is divisible, not, therefore, simply because of magnitude or something entailed by magnitude is a body productive of motion. Nor is primitive matter productive of motion, because it is itself passive. It is therefore necessary that motion follow simply from the primitive form as from an efficient cause.