But that I set fire upon the beauty of the fields, this is the earth, which is that matter from which God made man; and what shines in the waters, this is according to the soul, for as water floods the whole earth, so the soul traverses [/permeates*] the whole body. That truly I blaze in the sun and in the moon, this is intelligence (while the stars are the innumerable words of the intellect).
Quod autem super pulchritudinem agrorum flammo, hoc terra est, quae materia illa est de qua Deus hominem fecit; et quod in aquis luceo, hoc secundum animam est, quia sicut aqua totam terram perfundit, ita anima totum corpus pertransit. Quod vero in sole et in luna ardeo, hoc rationalitas est (stellae autem innumerabilia verba rationalitatis sunt).**
(**Punctuation modified from PL to match CCCM 92)
The trinity that is in man - body, soul, and spirit - are one, just as the light coming from the sun, shining on the waters, and blazing on the fields are one. The sun is separated from the earth and the waters, but one with them in the illumination - the sun actively illuminating, the waters and the earth passively illuminated. That is the role of the human intellect, though it is not mixed materially with the body, it's light is reflected in the soul and the body.
The earth and the waters are two different elements, but become one combined as the water penetrates and permeates the earth. This is an image of the unity of the body and the soul. The soul vivifies from head to toe, out to the fingertip, and in all the senses. The soul is like the horizon between the body and the spirit.
The sun burns brightly - this is an image of intelligence. At night, the lesser lights govern the world from above - the moon with the light of the sun, the stars with each their own humble light. The glowing light of the sun is not the only light to be had - the intellect not only judges - it also assimilates and reasons. The innumerable other stars are the concepts (verba) we have formed, and by which we also have light - though a much lesser light. I would say that the moon is comparable to the analogical concept we have of being - the greatest light we can have, which depends nonetheless entirely upon the light of being itself.
To interpret spiritually the parallel nature of this vision, we must recognize that Charity is speaking about herself, while at the same time speaking about Creation and man. Charity brings light to the body - "The lamp of the body is the eye. If therefore your eye is good, your whole body will be full of light." (Mt. 6:22) Charity is the true light for our eyes: it is what allows us to perceive the goodness that illuminates even our flesh. The soul too seeks out this light, "I sought him whom my soul loves: I sought him, but I found him not." (Cant. 3:1) "I found him whom my soul love: I held him, and would not let him go." (Cant. 3:4) The light of love is that upon which our soul depends in order to be like the water that permeates the earth. "My soul thirsts for you, my flesh longs for you in a dry and thirsty land, where no water is." (Ps. 63:1) "Like cold water to a weary soul, So is good news from a distant land." (Pro. 25:25) The flesh and the soul of man long for the light that is both in the spirit of man by his creation (his intellect), and essentially is the light of Charity - the Creator.