On Breath

​9 Those who deny that heat is what active in bodies, or [assert] that the cutting action of fire is some single movement and power, do not speak correctly. For it does not do the same thing to all inanimate things either, but some it condenses, others it rarefies, and melts, and others it solidifies. And in animate things indeed we must assume in this way, as if seeking the fire of nature just like that of art; for indeed in arts, a different fire produces the work of the goldsmith, the coppersmith, the carpenter, and the cook. But perhaps it is truer that the arts [produce them]; for they use [fire] as an instrument, softening, melting, and drying, and some also shaping. This same thing indeed applies to natures as well; whence indeed also their differences from one another. Therefore, it is ridiculous to judge by reference to what is external; for whether heating and being fired is separating, or thinning, or whatever it is, it will have different effects for those who use it. But while arts use it as an instrument, nature uses it also as matter. Now this is not difficult, but rather to conceive nature itself which uses it, which will render both the sensible affections and the proportion. For this is no longer of fire or of breath. That such a power is mixed with these is indeed wonderful. And further, this same wonderful thing is also concerning the soul; for it exists in these. Therefore, it is not bad to bring to the same thing, either simply or as some part, that which fashions and that which always effects the similar movement to exist. For indeed nature [is that] from which also generation [comes]. But what indeed is the difference of the individual heat, whether as an instrument, or as matter, or as both? For the differences of fire are according to the more and less. And this is almost as in mixture and unmixture; for the purer is more. And the same account applies to the other simple elements as well. For it is necessary, since the bone and flesh of a horse and an ox are different, either that they are from different things or differ in their use. If then they are different, what are the differences of each of the simple elements, and what [is the proportion]? For these are what we are seeking. But if they are the same, they would differ in their proportions. For one of the two is necessary, just as in other things; for the mixture of wine and honey is due to the substrate, but that of wine itself, if indeed it is different, is due to the proportion. Therefore Empedocles also [said] that the nature of bone is simply one. If indeed all had the same proportion of mixture, those of a horse, a lion, and a human ought to have been indistinguishable. But now they differ in hardness, softness, density, and likewise flesh and the other parts. And further, the parts in the same animal differ in density and rarity and the others, so that there is not the same mixture. For thick and thin and great and small would be in quantity, but hard and dense and their contraries in the quality of the mixture. And it is necessary for those who thus speak to know how the fashioning cause would be different, both by this being more or less, and by being fired by itself, or as mixed or in another. For it is mixed in at the same time and produces the work of nature. Therefore, the same account applies to flesh as well; for there are the same differences, and almost also concerning vein and artery and the rest. So that one of the two is necessary, either the proportion of these according to mixture is not one, or we must not grasp the proportions by hardness and density and their contraries.