It seems that by merely learning what is good and applying that knowledge one can be sure that one is doing good.
But doing good things requires that one should also have knowledge of contingent matters. But contingent matters are infinite according to St. Thomas Aquinas. Therefore, since infinite things are uncertainly known, then doing good things can only be done uncertainly.
But then, how could virtue be defined as right action in accord with good reason? For if it was, then we could never be virtuous since we can’t do anything but uncertainly.
Yet we know that this is a true definition so perhaps contingent matters are somehow not infinite.
So I will ask a few other questions that are related to my main one: (1) are contingent matters infinite? (2) are particular events knowable in some way? (3) Does our universal knowledge allow us to understand particular things and to impose a certain finitude upon them or is it essentially unable to comprehend the infinite particulars of life?
But maybe there is an answer to my question which is sufficient. We should not insist on mathematical precision and certainty in moral science. But moral practice is just an application of the ideas of moral science and therefore we should not expect moral practice to be so certain either. Is that a good answer? Even if it is, I’m curious to see what answers people might have to the above questions 1-3?