Boethius defined chance in terms of epistemic uncertainty

Reading Boethius's "The Consolation of Philosophy", I've been repeatedly struck by Boethius showing knowledge of ideas that I'd wrongly assumed only had a later origin. This reminds me that we should not underestimate the "ancients", although he is far closer to us than the true ancients, two hundred thousand years or more before.

Here he is defining "chance" in terms of epistemic uncertainty, after nodding to arguments from the ancients that there are not chance occurrences:

We can define chance, then, as the unexpected result of causes that come together of things that were done for some other purpose.

(Emphasis added by me.) He credits Aristotle's Physics as the source of this idea.

Another example that surprised me was him mentioning the problem of evil -- how can an omnipotent God allow there to be evil in the world? His answer, at least in the translation I'm looking at from David Slavin, is that "evil is nothing".

This other translation captures the same thing:

‘Nobody would care to doubt that God is all-powerful?’
‘At any rate, no sane man would doubt it.’
‘Being, then, all-powerful, nothing is beyond His power?’ ‘Nothing.’
‘Can, then, God do evil?’
‘No.’
‘Then evil is nothing, since it is beyond His power, and nothing is beyond His power?’

He also makes many arguments that at least have the flavor of an ontological argument. Again from that other translation:

‘Now consider,’ she continued, ‘where it lies. The universally accepted notion of men proves that God, the fountain-head of all things, is good. For nothing can be thought of better than God, and surely He, than whom there is nothing better, must without doubt be good. Now reason shews us that God is so good, that we are convinced that in Him lies also the perfect good. For if it is not so, He cannot be the fountain-head; for there must then be something more excellent, possessing that perfect good, which appears to be of older origin than God: for it has been proved that all perfections are of earlier origin than the imperfect specimens of the same: wherefore, unless we are to prolong the series to infinity, we must allow that the highest Deity must be full of the highest, the perfect good. But as we have laid down that true happiness is perfect good, it must be that true happiness is situated in His Divinity.’

The reasoning in these sections bothers me because it seems to trade on different meanings of the terms involved: "existence", "nothingness", etc. I don't recall Boethius addressing this possibility, but he does recognize the counterintuitivenss of some of his conclusions; he notes that if you cannot question either the premises or the reasoning from them, then you should accept the conclusion, which is something I heard one of my intro philosophy professors say around 1500 years later.

Do we need to define evil away to "remain Stoic"? I think there are good practical reasons to remain calm in the face of adversity, as in the Serenity Prayer:

God, grant me the serenity to accept the things I cannot change,
the courage to change the things I can,
and the wisdom to know the difference.

Before reading Boethius, I had a vague idea Stoicism was about this, maintaining calm despite the circumstances, a practical philosophy. But Boethius ultimately seems to be arguing that there is no such thing as adversity? To me, that weakens the appeal a bit.