Bern, Burgerbibliothek, Cod. 402

...inflamed, and those in the earth, for all are either of such a quality or of fire, or they are a mixture of both liquid and fire, or they are all of the two. Simply put, always and every burning thing, just as generation is peculiar like motion, is in a way destroyed as it is generated, and it perishes along with the depletion of the fuel. This was also what was said by the ancients, that fire always seeks nourishment, as it is impossible for it to remain without matter. This appears absurd to say about it, and as if an arche first principle could not exist without matter, for it is not simple in this way, nor prior to the underlying subject and matter, unless there is such a nature in the first sphere itself, so that heat is unmixed and pure. But in this way, it would not burn. This is the nature of fire, except for the qualities and differences. The first is pure and unmixed, while that around the sphere of the earth is mixed and always in a state of generation. The arche first principle is naturally prior to its generation, or from the underlying subjects, when they become in such motion and disposition toward one another as we were just speaking of, perishing at their peak. For such motion and alteration is somehow related to the nature of heat. For the sun, which creates all these things—again, the sun's [nature] or the idea of fire—has the greatest difference, being a kind of principle and coming toward them. For light comes from this, as does the generative heat in animals and plants. The connection of this earthy and burning fire is made through this. Many, therefore, who kindle fire suppose the radiance to be from the sun. But the mixture is fire, not light without fire.

sphere

of it