And the terms “radiance” (diyāʾ), “light” (nūr), and the like are sometimes used for a self-luminous body itself—such as the sun, the moon, or fire. The Exalted said:

“He is the One who made the sun a radiance and the moon a light” (Yūnus 10:5),

and He said:

“and We placed therein a blazing lamp” (al-Nabaʾ 78:13).

Thus the Almighty called the sun a “lamp” and a “radiance” because, besides giving illumination and brightness, it also produces heat and burning; in this respect it is more akin to fire, unlike the moon, for the moon, though it gives light, provides no warmth. Hence His statement: “He made the sun a radiance and the moon a light” (Yūnus 10:5).

The point here is that words like radiance and light may denote either the self-subsistent luminous body—such as the sun, the moon, or fire—or the ray that, because of that body, appears in the air and on the earth. This second meaning is an accident inhering in something else: it is neither the body itself nor an attribute residing within that body, but a contingent effect produced by it.

Accordingly, the ray that is the light found on water, clay, air, and the like is an accident existing in something else and is in no way identical with that substratum.

Therefore, even if the Nestorians, who say that the human nature (nasūt) and the divine nature (lahūt) are two essences with two distinct natures, one of which indwelt the other, were to employ this analogy, it would still be invalid; for the sun itself never indwelt anything else, nor did its volition merge with the volition of another