St Augustine does not encourage us to be foolish. We also should not be so foolish is to make such loft declarations with so little knowledge.
I disagree that we have little knowledge. If, however, someone comes up with the hypothesis that our dating science is completely and totally rubbish (whether motivated by his not-revealed interpretation of Genesis or not) and wishes to test this hypothesis via either the methods of science or something that actually is revealed and not just his opinion about what is revealed, fine. But given that it is specifically said that either position is ok for Catholics to hold, revelation will not settle the debate, and given that no one else is beholden to his interpretation of Genesis, if he fails on that front or if he’s dealing with a non-Christian, then he’s left with empirical methods. (And even if revelation did settle the debate, he should pursue the empirical methods without bias, because truth does not contradict truth and so he would eventually arise at evidence that the wider community would accept. That science cannot answer the question is ruled out by the fact that science already has a large body of evidence.) If he makes a sound empirical argument, then science will change.
And it actually will change, assuming he makes a sound scientific argument - the idea that “mainstream” science will just reject such advancements for ideological reasons is false. Sociology and psychology, and even ecology and various “macro” systems in general
may be plagued by such things, but when you get to the level of basic physics on which things like dating based on half lives of various radioactive isotopes live, there isn’t much room for such rejections in the face of actual science. Witness Fr. Lemaitre and the (near) destruction of the steady state view of the universe.
To attempt to project Augustine a bit further into this situation: I would guess that his point of view would be that if you’re going to challenge a scientific point of view, especially among non-Christians, do it with science - and not by claiming that your own personal interpretation of scripture is above all of the reasoning that everyone else has done. Because it’s possible that your interpretation is wrong, that their logic is right, and that you’ve been making the writers of scripture look like fools.
If it were an infallible interpretation of Scripture, that would be a different matter. But it’s not. It’s your opinion. And preaching your opinion about Scripture as though it were set-in-stone, revealed-by-God fact to people who think your opinion is silly denigrates their perception of Scripture (and your religion in general) to no good purpose.
Someone said something about “but science has put its foot down.” Science never puts its foot down irrevocably, but it does require that the lifting of the foot be motivated. This is more of a case of the young-earther putting his foot down because of his own opinion about what Scripture means and then refusing to move it come Hell or high water.
Again, I am not here talking about those who think it likely that the days are literal 24-hour days and so hold to that view keeping in mind that it is not known with certainty to be true, I am talking about the person who ascribes a certainty to this view that paints all who disagree as not taking scripture seriously enough because they dare to disagree with his opinion about what scripture says, or as denying something that is certainly known to be true, or some similar nonsense.
(For the record, I would also say the something similar about people who say that they know with the certainty of faith that the 24-hour days are false, but we haven’t had any of those yet - or if we have, I haven’t read their posts.)
Believe what you want, by all means, but do not claim that the full authority of the word of God is certainly behind you because you do not have such certainty.
The difference boils down to empirical evidence vs non-empirical.
More correctly, it’s “empirical evidence” vs “something that some people think may be evidence, but need not be really.”
Again, if we knew that the Genesis passage were evidence for a young earth view, then we would know that it was to be interpreted in that manner, and if we knew that then it would be a known truth of the faith.
But. It. Is. Not.
Otherwise there would not be freedom to hold either opinion.
And there is.