But if, laying aside those servile habits and opinions to which we have enslaved ourselves, we must frankly and fearlessly deliver our judgment, it seems clear to me, that there is not any part of the universe which has a peculiar and separate rank, situation, or motion, that can simply be said to be natural to it. But when every thing exhibits and yields up itself to be moved, as is most profitable and fit for that for whose sake it was made and to which it is by Nature appointed,—suffering, doing, or being disposed, as is most expedient and meet for the safety, beauty, and power of the same,—then it appears to have its place, motion, and disposition according to Nature. As a proof of this, we may observe that man, who, if any thing in the world be so, is made and disposed according to Nature; has upwards, especially about his head, heavy and terrestrial things, and about the middle of his body such as are hot and participate of fire; of his teeth also some grow upwards and some downwards, and yet neither the one nor the other are contrary to Nature; neither is the fire which shines in his eyes according to Nature, and that which is in his heart and stomach against it; but it is in each place properly and beneficially seated. Moreover, consider the nature of all shell-fishes; and, that I may use the words of Empedocles, Look on the crabs, the oysters of the sea, And shell-fish all, which heavy coats enfold, The tortoise too with arched back, whom we Covered with crust, as hard as stone, behold. View them but well, and plain it will appear, They hardened earth above their bodies bear. And yet this crust, stone-like, hard, and heavy, as it is thus placed over their bodies, does not press and crush their natural habit, nor on the contrary does their heat fly upwards by reason of its lightness, and vanish away, but they are mingled and composed one with another, according to the nature of each one.