For you may reasonably speak of motion not existing. And what, also, is the matter of motion? Is it straight or circular? Or does it take place by a process of change, or by a process of generation and corruption? The circular motion, indeed, is so orderly and composite, that it is ascribed to the order of all created things; nor does this, in the Manichæan system, appear worthy to be impugned, in which move the sun and the moon, whom alone, of the gods, they say that they venerate. But as regards that which is straight: to this, also, there is a bound when it reaches its own place. For that which is earthly ceases entirely from motion, as soon as it has touched the earth. And every animal and vegetable makes an end of increasing when it has reached its limit. Therefore the stoppage of these things would be more properly the death of matter, than that endless death, which is, as it were, woven for it by them. But the motion which arises by a process of generation and corruption it is impossible to think of as in harmony with this hypothesis, for, according to them, matter is unbegotten. But if they ascribe to it the motion of alteration, as they term it, and that by which we suffer change by a quality affecting the sense, it is worth while to consider how they come to say this. For this seems to be the principal thing that they assert, since by matter it comes to pass, as they say, that manners are changed, and that vice arises in the soul. For in altering, it will always begin from the beginning; and, proceeding onwards, it will reach the middle, and thus will it attain unto the end. But when it has reached the end, it will not stand still, at least if alteration is its essence. But it will again, by the same route, return to the beginning, and from thence in like manner to the end; nor will it ever cease from doing this. As, for instance, if a and g suffer alteration, and the middle is b, a by being changed, will arrive at b, and from thence will go on to g. Again returning from the extreme g to b, it will at some time or other arrive at a; and this goes on continuously. As in the change from black, the middle is dun, and the extreme, white. Again, in the contrary direction, from white to dun, and in like manner to black; and again from white the change begins, and goes the same round.
 to atakton.