The Philosophy of Roger Bacon

greater things therefore. If, therefore, there is no natural light except in proportion to its own speculative? nature, because it is dense and water is drawn along? so that it may speak of someone's [vision] regarding it, it then appears by itself in its own...
sphere

...which is crossed by air, and the more rare it is, the more it penetrates it, for the sun in [the hand of the good?] and flame instead of light because just as the first [proposition] might be seen of the senses creature? and is summoned and ought in dense nature to strike again because it will be seen what is taken away before [the eyes] in a game and what is seen in this world. Therefore, it is said that there is one [nature] of fire and of the sun and stars because of this, and the heat it has drawn out ought to be of the same species species; in medieval science, this refers to the specific essence or "kind" of a thing because its passion passio; the effect or quality experienced by an object, or the way it is "acted upon" has the same cause, and so fire and the heaven will not be of a different nature or species. For a greater force is closer, and another might dissolve the points of the sun for another view of the world, so that the heaven may be of a fiery nature; and through this, the effects that fall to them will have the same cause in both the fire and the stars.

If, however, there is not one species, and therefore the stars are remote and any density of sight is the cause, they will change in both places because there is not one species in either fire or the heavens. [Regarding] heat, I provide the understanding and the proper nature of a thing such that it is not a "passion" of that thing and the rest, because one thing heating another—such an effect has a different species which comes from the substance of the sphere. Against this? it is clear by those qualities, although in the same space where there are different kinds of qualities. Quality, however, causes this act; and whether heat in fire or in [the sphere] itself might be persuasive in some place—not so much in itself, but it will be certified later.

If it is said that by reason "upward" is that which is most light original: leue; meaning light in weight or buoyant, rather than bright, just as water equivocally it seems here that then "upward" will be just as it. For when something is light, then regarding the light upward—which by nature is to be moved upward as far as the extent of the heaven—and so concerning natural light which is buoyant just as it locates [itself] and not the whole. And truly, that which belongs to the heaven is entirely "upward" as if toward an "upward place"; for if it be light, it would be [moving] toward a certain amount now by rectilinear motion motu recto; motion in a straight line, which Aristotle attributed to the four elements (up or down) rather than the circular motion of the heavens and it is called upward.

If it is said that it is positioned in a place as water is said to return, and in the metheora; a reference to Aristotle's "Meteorologica," a text concerning phenomena in the upper atmosphere, just as the "downward" place will be the water, concave by its own nature toward the center of the world, and the earth toward the center.