Further, Genesis 1 tells us that the thrice-best and greatest God first created those universal principles, namely water—as the Hebrew word Schamaym signifies, and certainly not some unformed, unordered mass. From it he separated earth and air. In accordance with his hidden wisdom, he willed that fire should remain hidden in them. But he established that particular thing, light, which, after separating it from darkness, he called day, and the darkness night.

To differentiate this universal order and the time which was then everywhere equinoctial, and to introduce the succession of seasons, God Most High created the two great lights in the firmament: the greater to rule the day, the lesser to rule the night, and the stars. This plainly shows that light and day belong to one created substance and natural order, while the stars belong to other created substances and another natural order. One was not transformed into, reduced to, or distributed among the other, as some dream and prattle, although one is governed through the other. For God’s words and decrees are immutable.

The earlier decree, “Let there be light,” was not changed in the slightest by the later decree, “Let there be lights.” Nor was the universal order and division of day and night changed in its being, but only modified; day is now governed in particular through the sun’s rising and setting, as stated. Light must therefore still be the same light as on the first day of creation. Indeed, the decree “to rule the day” necessarily presupposes the existence and continuation of what the sun is to rule—the light or day expressly named in the decree. For what does not exist can have neither qualities nor accidents.

God created nothing that he did not will to preserve. No creature has ever changed its being or ceased to exist from the beginning of creation to this present hour. Thus the modern writer S. is mistaken. In his Institutions of Natural Philosophy, Book VI, chapter 4, question 9, page 531, he expressly writes that light was a substance because it was the terminus of an act of creation. On the following page he likewise admits that the terminus of creation was always a substance; yet elsewhere he attempts to maintain that light is a quality. Since it was a substance, the principles cited above require that it still be a substance.

For in the passage already cited from Job 38, motion and locality are ascribed to light, circumstances that presuppose substance according to the principles just stated. If light or day existed in the sun, as you and your authority suppose, how could the sun rule over it? If it existed in the stars, night would not be night, and night and day would not be separated. If light subsisted in any other body, we could see all such bodies by night just as well as by day, without a candle.

As to the second point, I need not mention those who posit three kinds of substance. It is enough that I have proved almost to weariness that light is a substance and inheres in no body. Your argument therefore turns against you. Since light is seen, since nothing incorporeal is perceptible to our eyes and sight in this mortal condition, and since there is no third possibility, light must be corporeal. I am not ashamed to maintain this. God has created nothing through a spoken word, a particular word and decree, that is wholly incorporeal. I therefore say that light is, or possesses, a supremely transparent and subtle body.

Nor, as to the third point, does your clarification seem to present an obstacle. I mean natural light, specifically what God called Day and you call primordial light; this alone is intended here. I do not mean what you call an accident, quality, and most subtle affection of a luminous body, by which the world and its various bodies become perceptible, varying according to its subjects. Nor do I recognize your “later” light, unless it means the universal fire already mentioned, which gives all things splendour and colour. In the stars this is commonly called radiance, in animals fat, in plants oil, and in minerals Sulfur. It cannot possibly be an accident, since it is one of the principles or elements of which, as is well known, all visible things consist.

As for the distinction between ordinary and extraordinary light, and your proposition that on the first day light inhered in the surface or some subtler part of the waters, on the second and third days in the air or entire heavenly expanse, and on the fourth, after the creation of the luminaries, was imparted to sun, moon, and stars: these are mere assumptions of the point to be proved, contrary to Nature’s reason and order. Where did God create anything extraordinarily? It is also utterly absurd that one and the same accident—supposing, without granting, that light is an accident—should inhere now in this body or subject, now in that, and then in another.

I rest entirely upon these foundations, which prove more than sufficiently that light is a substance. I have no wish to investigate further or plunge into the labyrinth of Aristotle’s volumes and those of other pagan philosophers and their imitators. Nevertheless, I wish to add what substance means in natural philosophy. Substance is said to be a pure and simple being that admits no contrariety into itself.

I shall pass over the higher bodies and speak only of the lower. These consist of two parts: substance and residues. The latter part is accidental, the former essential. I called substance a pure being to distinguish it from the residues, which are wholly impure. According to de Nuysement, the evil of corruption that followed God’s curse for the sin of our first parents attaches to those residues, not to substance. Substance considered in itself is pure. Although in every lower body the residue exceeds the substance, mingles with it, and contaminates and distorts its purity, it can nevertheless be separated through the intervention of Art.

I called it simple. Although every substance consists in three principles, none is first or highest, none last or lowest. Even if they can be separated, they cannot be divided essentially: each is always found in its companion.

I said that it admits no contrariety into itself, referring to its property. As de Nuysement attests, substance has this property of admitting no contrariety; otherwise the Art could not render it pure and free from corruption. Yet we see this daily in our Art. By God’s grace I myself know and have observed in practice that our Mercury receives into itself only what is homogeneous with its own essence.