"For, as usually happens when men see unfavourable dreams, and can make nothing certain out of them, when any event occurs, then they adapt what they saw in the dream to what has occurred; so also is mathematics. For before anything happens, nothing is declared with certainty; but after something has happened, they gather the causes of the event. And thus often, when they have been at fault, and the thing has fallen out otherwise, they take the blame to themselves, saying that it was such and such a star which opposed, and that they did not see it; not knowing that their error does not proceed from their unskilfulness in their art, but from the inconsistency of the whole system. For they do not know what those things are which we indeed desire to do, but in regard to which we do not indulge our desires. But we who have learned the reason of this mystery know the cause, since, having freedom of will, we sometimes oppose our desires, and sometimes yield to them. [861] And therefore the issue of human doings is uncertain, because it depends upon freedom of will. For a mathematician can indeed indicate the desire which a malignant power produces; but whether the acting or the issue of this desire shall be fulfilled or not, no one can know before the accomplishment of the thing, because it depends upon freedom of will. And this is why ignorant astrologers have invented to themselves the talk about climacterics as their refuge in uncertainties, as we showed fully yesterday.

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Footnotes:

[861] [This argument from human freedom is the favourite one throughout.--R.]