292 show that he is ignorant of where the slowness and speed of motion comes from. For this is not valid, A bag filled with tow is heavier in air than a little bit of lead, hence in air it will go down faster: for an idiot would not say this, nor any one who has understood the things that have been said above.Concerning fire one must reason in the following way: for a lot of fire will be heavier than a little bit of air; not however in air, where fire has no heaviness, but in another place where fire also exerts weight, as would be the case in a void or in a medium lighter than fire.
By Hercules! it is disgusting and shameful that words must be spouted to untangle such childish arguments as well as such crass subtleties as those which Aristotle crams into the whole of Book IV of the De caelo against the ancients: they are without strength, without learning, without elegance, without appeal, and anyone who has understood the things that have been said above, will recognize their fallacies.As when he says, We see that earth is below all things, but fire is above everything; Aristotle must have had the eyes of Lynceus{1}, if he has seen whether or not there is in the bowels of the earth something heavier than earth, and whether above fire their is a lighter body. But, without the eyes of Lynceus, someone who is blind will be able to see that there are many things heavier than earth, such as all the metals, on which, when they are liquified, earth floats, as on the one called quick-silver; and not only is earth lighter than quick-silver, it is more than ten times as light. How, then, can the metals take their heaviness from earth, if they are much heavier than earth; and moreover, if they were constituted from earth, water, air, and fire, would they not have to be much lighter than earth alone?It is therefore evident that there exist many things heavier than earth.Therefore when he says: The contrary places are two, the center and the extremity, taking as the extremity the concave sphere of the moon; hence it must be that the things in those places are contraries; which will not be the case, unless earth be assumed to be deprived of all lightness, and fire to be devoid of all heaviness: an argument that has no neccessity whatsoever; and even if it had any, it is in the same way that the concave sphere of water and of air is in opposition to the center, as is the concave sphere of the Moon; and yet, the things that are under the concave sphere of air are not deprived of all heaviness.{1}But what he says concerning the lightness of fire, saying {1} that, if air is removed from underneath, fire will not go down, like air when water is removed from underneath, is in need of demonstration: because Aristotle has not proved it, unless you say what he has said {2}, Just as earth does not go up in the small cupping glasses of physicians because it is very heavy, so fire will not go down because it is very light.But the ratio has no worth: for, it is not because