On The Heavens   

was impossible. Suppose that the world was formed out of elements

which were formerly otherwise conditioned than as they are now. Then

(1) if their condition was always so and could not have been

otherwise, the world could never have come into being. And (2) if

the world did come into being, then, clearly, their condition must

have been capable of change and not eternal: after combination

therefore they will be dispersed, just as in the past after dispersion

they came into combination, and this process either has been, or could

have been, indefinitely repeated. But if this is so, the world

cannot be indestructible, and it does not matter whether the change of

condition has actually occurred or remains a possibility.

Some of those who hold that the world, though indestructible, was

yet generated, try to support their case by a parallel which is

illusory. They say that in their statements about its generation

they are doing what geometricians do when they construct their

figures, not implying that the universe really had a beginning, but

for didactic reasons facilitating understanding by exhibiting the

object, like the figure, as in course of formation. The two cases,

as we said, are not parallel; for, in the construction of the

figure, when the various steps are completed the required figure

forthwith results; but in these other demonstrations what results is

not that which was required. Indeed it cannot be so; for antecedent

and consequent, as assumed, are in contradiction. The ordered, it is

said, arose out of the unordered; and the same thing cannot be at

the same time both ordered and unordered; there must be a process

and a lapse of time separating the two states. In the figure, on the

other hand, there is no temporal separation. It is clear then that the

universe cannot be at once eternal and generated.

To say that the universe alternately combines and dissolves is no

more paradoxical than to make it eternal but varying in shape. It is

as if one were to think that there was now destruction and now

existence when from a child a man is generated, and from a man a