Book, Paragraph

 1   V, 6 |            moving may be natural or unnatural, in the other changes this
 2   V, 6 |             not now natural and now unnatural, for convalescence is no
 3   V, 6 | convalescence is no more natural or unnatural than falling ill, whitening
 4   V, 6 |        whitening no more natural or unnatural than blackening; so, too,
 5   V, 6 |          natural while the other is unnatural, nor is one increase contrary
 6   V, 6 |            is natural and perishing unnatural (for growing old is natural),
 7   V, 6 |           to be natural and another unnatural. We answer that if what
 8   V, 6 |           happens under violence is unnatural, then violent perishing
 9   V, 6 |           then violent perishing is unnatural and as such contrary to
10   V, 6 |           certainly contrary to its unnatural motion. Similarly with remaining:
11   V, 6 |            motion naturally. So the unnatural remaining of a thing is
12   V, 6 |          will be natural, the other unnatural.~Here, however, the question
13   V, 6 |           opposite state of rest to unnatural as well as to natural motions.
14   V, 6 |          case: for just as there is unnatural motion, so, too, a thing
15   V, 6 |           too, a thing may be in an unnatural state of rest. Further,
16   V, 6 |        things have a natural and an unnatural motion, e.g. fire has a
17   V, 6 |        natural upward motion and an unnatural downward motion: is it,
18   V, 6 |           motion: is it, then, this unnatural downward motion or is it
19   V, 6 |             motion of fire as being unnatural. The same is true of the
20 VIII, 4|      natural, in others violent and unnatural. Thus in things that derive
21 VIII, 4|             cases natural, in other unnatural: e.g. upward motion of earthy
22 VIII, 4|         downward motion of fire are unnatural. Moreover the parts of animals
23 VIII, 4|           are often in motion in an unnatural way, their positions and
24 VIII, 4|        cases in which the motion is unnatural: we are left with those
25 VIII, 4|            it is when the motion is unnatural, whence their motion is
26 VIII, 4|        motion is violent when it is unnatural, and natural when it brings
27 VIII, 4|         motion is either natural or unnatural and violent, and all things
28 VIII, 4|         whose motion is violent and unnatural are moved by something,