The "act of that which is in power" also seems a ridiculous phrase, though it is no more so than the one just noticed. Matter may become whatever you will--fire, earth, water, vapor, metal, mineral, animal, tree, flower. This is all that is meant by the expression, _act in power_. So that there was nothing ridiculous to the Greeks in saying that motion was an act of power, since matter may be moved; and it is very likely that Aristotle understood thereby that motion was not essential to matter.
Aristotle's physics must necessarily have been very bad in detail. This was common to all philosophers until the time when the Galileos, the Torricellis, the Guerickes, the Drebels, and the Academy del Cimento began to make experiments. Natural philosophy is a mine which cannot be explored without instruments that were unknown to the ancients. They remained on the brink of the abyss, and reasoned upon without seeing its contents.
His researches relative to animals formed, on the contrary, the best book of antiquity, because here Aristotle made use of his eyes. Alexander furnished him with all the rare animals of Europe, Asia, and Africa. This was one fruit of his conquests. In this way that hero spent immense sums, which at this day would terrify all the guardians of the royal treasury, and which should immortalize Alexander's glory, of which we have already spoken.
At the present day a hero, when he has the misfortune to make war, can scarcely give any encouragement to the sciences; he must borrow money of a Jew, and consult other Jews in order to make the substance of his subjects flow into his coffer of the Danaides, whence it escapes through a thousand openings. Alexander sent to Aristotle elephants, rhinoceroses, tigers, lions, crocodiles, gazelles, eagles, ostriches, etc.; and we, when by chance a rare animal is brought to our fairs, go and admire it for sixpence, and it dies before we know anything about it.
Aristotle expressly maintains, in his book on heaven, chap, xi., that the world is eternal. This was the opinion of all antiquity, excepting the Epicureans. He admitted a God--a first mover--and defined Him to be "one, eternal, immovable, indivisible, without qualities."