afterwards in air, although air is more subtle than water?</s>
<s id="id.4.0.0.87.05">How, then, will it ever be true that natural motion is necessarily faster in a more subtle medium than in a thicker one? {1}</s>
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<s id="id.4.0.0.88.00"/>
<s id="id.4.0.0.88.01"> Now here it does not escape me that there is a great number of more recent philosophers who profess to know things which they know more by relying on the authority of others than by demonstration: these persons, if they heard such things, would immediately undertake to reply, and they would be satisfied to throw in a couple of words, even if they had nothing to do with the subject; for a little latter they would add, Such an opinion has been more than sufficiently and fully refuted before; and it is with similar turgid terms that they persuade themselves and their listeners, who are even more ignorant than they, of their opinions.</s>
<s id="id.4.0.0.88.02">For to these people, if they were to hear my arguments, and retorted that my reasoning is not conclusive, because I speak now of upward motion and now of downward, which is contrary to Aristotle's intention, or brought forward similar remarks without any soundness, {1} to these people, I say, it would seem that my opinion has been more than sufficiently refuted. </s>
<s id="id.4.0.0.88.03">But so much for them: let it be sufficient for me that I would have forestalled such a response of theirs, when I added a second example {1}, which only talks of one motion.</s>
<s id="id.4.0.0.88.04">It must therefore be concluded that the following is entirely false, namely that the slowness or the swiftness of motion results from the thickness or the subtlety of the medium. </s>
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<p>
<s id="id.4.0.0.89.00"/>
<s id="id.4.0.0.89.01">Secondly: Aristotle has taken for granted as if it were known, that the speed of one motion has the same ratio to the speed of a second motion, as the subtlety of the first medium has to the subtlety of the second medium. </s>
<s id="id.4.0.0.89.02">This, Aristotle has not demonstrated, and he even skillfully avoided it: for to have taken pains to do so would have been in vain, since it is not demonstrable, and, not only not demonstrable, but actually false. </s>
<s id="id.4.0.0.89.03">For, even if it is conceded that subtlety is the cause of swiftness, it will follow, to be sure, that in a [medium of] greater subtlety, the swiftness will be greater; but it still will not follow that the swiftnesses and the subtleties increase in the same ratio. </s>
<s id="id.4.0.0.89.04">And, to use Aristotle's way of speaking, the subtlety of air would have no ratio to the subtlety of water: for, as an example, {1} wood goes down in air, but not in water; hence the swiftness in air will have no ratio to the swiftness in water. {2}</s>
<s id="id.4.0.0.89.05">In order that this may appear clearer than daylight, </s>
