Had an interesting set of discussions in and out of class regarding the question of evil. A student formulates the question thus:
If one had full knowledge of the evil of X, would it be possible for that one to do X?
I say yes; she says no.
Of course, one would not be likely to do X, but still free to do so. Such a state of knowledge could best be compared to that of the angels at their creation, but of course, not exactly since angels have no sensitive appetite (passive, emotional part). Not exactly like pre-lapsarian Adam either, since then Adam had no inclination to sin, but he did not have anything resembling full knowledge, rather his problem was that quite the opposite was the case. Angels had then no need, desire, compulsion, attraction to sin, nor would they see any advantage in it; nor can it be said that the fallen angels currently experience such desire, but perhaps fascination and other words that connote intellectual attraction.
A man of complete knowledge is perhaps hard to conceive or even precisely define. Let us agree that we just mean by it a knowledge that cannot be exceeded in terms of its vastness by a finite human mind. It fills the mind. Will such a thing ever exist? Not in the way I mean it, for, the completeness of the knowledge that the comprehensors will enjoy in heaven is more importantly beatific: the knowledge of seeing God that brings joy. How is knowledge productive of joy? We need to see how they stand in relationship if we are to answer our current question. Since, if knowledge makes one joyful inevitably, and great knowledge greatly pleases, it would then be nearly impossible for one of great knowledge to sin. The complete knowledge of heaven makes sin impossible. But this knowledge is perhaps not, objectively speaking, as great as that of the fallen angels before their fall. So, there must be different kinds of knowledge; all knowledge cannot stand in relation to joy in the same way. For, in terms of the human soul of Christ, St. Thomas seems to only speak of the kind of knowledge that gives Christ's soul joy as the beatific knowledge, not His infused nor His acquired knowledge. We have acquired knowledge; that is the knowledge appropriate to our nature. If we read Thomas right, this type of knowledge does not lead to joy essentially. If that is the case, then it is clear that since knowledge does not lead to joy, knowledge will not strengthen our attachment to the good. If we become attached to the good as a result of our increase in knowledge it is not due to our increase in acquired (experienced) knowledge, but because God has infused some knowledge into us.
Is there an assumption in my young interlocutor that knowledge produces prudence, or at least a certain excellence thereof does? Prudence would be an intellectual awareness of how to secure and maintain my good, and would include an inclination to act according to it. It is a hybrid virtue (speculative: includes knowledge of the good; practical: includes knowledge of how to do the good; a moral virtue: includes an inclination to do it). The question is: does complete knowledge of the evil of X include the knowledge of prudence with respect to it? If it's truly complete, then, of course. But maybe not, if by knowledge you simply mean what can be written in a book. So, it's a matter of definition. I think my interlocutor meant 'book knowledge.' Yet, even if she did not, I still maintain my position, since one can sin even when one has the virtue that works against such sins.
In sum, my position is this: knowledge contributes to virtue, yes, but even so, virtue is no complete assurance against sin when virtue is incomplete, as it aways is in this life. One can always chose against what one knows. It is less likely the more fully prudence develops, but never rendered impossible. In our case, sensuality is a strong force, even against the force of our better judgment. And, what's more, intelligence is deceptive and somehow great knowledge still permits the possibility of us thinking that we know better than God. I'm not sure how this is so, but the case of the fallen angels proves this. In sum, even in the face of overwhelming proof to the contrary we can yet decide that a sin is something to be done. I did not say that we judge that a sin is not in this case a sin, but that we can simply decide that it is something to be done.