St. Thomas argues that the use of metaphor and image – which for him occurred chiefly in poetry but occurs in all fine art – was a kind of rational discourse. The testimony of artists is terribly mixed about this: on the one hand Dickens was quite clear that he wrote A Christmas Carol as a sort of argument; on the other hand artists bristle at the claim that they are moralists or that their art is an allegory for a larger point - and no one tends to experience art as though it were primarily an imperfect attempt at demonstrative or scientific discourse. So how is the use of an image a sort of rational discourse? Is it just “philosophy for the mob” or some other degraded thing?
Notice that St. Thomas is dividing various modes of rational discourse. The problem of the relation of poetry and science concerns the nature of a modal distinction, and strange way in which things that differ in mode are in one sense unified and in another sense opposed. Modal distinction always needs to be understood by two opposed accounts: one which unifies the things different only modally and another which opposes them.
To take a concrete example, it is difficult to read Dostoyevsky and not see him as persuading us to one particular answer to the consequence “If God does not exist, all is permitted”. But he is certainly not doing it in the mode that a moral scientist or metaphysician would use, and this difference in mode is a great consequence. When a metaphysician gets a hold of that consequence, he will cast God and moral prohibitions in metaphysical terms: God will become “the supreme value” or “the source of obligation” or, “an internalized voice of a parent” or “a construct invented for social order”. The discourse takes place in the infinite, wide open space of logical possibility. There is an indifference to any particular case, though not because what he concludes in irrelevant to it but because his mode of discourse doesn’t treat of it as particular. This mode of discourse makes Dostoyevsky’s question incredibly difficult to deal with: the infinite, wide open space of abstract discourse makes for too many counter-examples; it makes precision on what exactly the question is claiming difficult; it presupposes a great amont of previous metaphysical work; and the metaphysician’s indifference to the particular leaves off what is most significant in moral questions, making it seem that we are missing the heart of the manner. Most importantly, the sort of law that one speaks of when he asks if all is lawful apart from God is an interior, intimate and personal reality, and the scientific method does not strike anyone as the proper or poportionate tool to deal with such things. But, of course, Dostoyevsky does not raise or treat the problem in a demonstrative or scientific mode. He avoids the problem of the infinite counter-examples and indifference to the particular by not working within logical, abstract space but within the concrete space of the novel- for logical, abstract space is too unruly to raise the question in a precise way or deal with it in a satisfying way; but the space of the world created by Brothers Karamazov or Crime and Punishment gives the question an immediate force and a very clear answer. Most importantly, Dostoyevsky uses a tool that is more proportioned to manifesting interior, personal realities. The poetic mode of discourse gives Dostoyevsky a sort of algebra that can solve a problem very quickly and easily that Euclidian geometry could only solve with great difficulty, if at all. One simply sees that Raskolnikov or Ivan or Smerdyakov have a presence of God within them that both commands goodness and makes them human. Something is utterly and irretrievably lost when the philosopher reads Brothers K and then decides to try to deal with the question in the mode proper to his own discourse. Isn’t there something boring, futile, and vain about a bunch of philosophers all trying to figure out if Dostoyevsky is “right”? This does not mean that we cannot refute Dostoyevsky, but rather that such a refutation has to happen in the mode proper to poetry: and there really are such refutations – the comic book villain or suave, glamorous, unconflicted movie-villain is certainly one such. It is a contradiction in the world of Brothers K for there to exist a healthy, sane, otherwise normal person that relishes evil. If such a character were true in the mode that poetic discourse has truth (or if such a person could really exist), then Dostoyevsky would certainly be refuted.