This questions raises all sorts of interesting issues. I'm going tolimit my focus to the question of the relationship between morality andbeauty and avoid any discussion of more general questions relating totruth and the value of art. But there's a wealth of good literature onthe relation between morality and artistic value. See, for example, theessays in Jerrold Levinson (ed.), Aesthetics and Ethics, (Cambridge: CUP, 1998). But here are a few thoughts on beauty and morality.
Itis true that we sometimes talk of immoral beliefs being ugly. We mayalso characterize immoral actions as ugly and moral ones as beautiful.And character assessment is sometimes made in terms of beauty andugliness ; e.g., 'she has a beautiful soul'. But I'm tempted by thethought that these usages are metaphorical; that is, we are not reallymaking aesthetic judgments--we are not literally ascribing beauty tothese objects-- when we talk this way. Why? Well, beauty and uglinessin the paradigm cases are associated with perceptual experience. Themost uncontroversial cases of literal judgments of beauty involvethings that can be perceived. And the clearest cases in which we can besaid to experience beauty are rooted in perceptual experience. Forexample, our experiences of the beauty of the sunset, the painting, theflower, etc. are based on our perception of those objects.
Ourcharacterizations of immoral beliefs as being ugly doesn't seem to meto be based on their being able to be perceived. Neither perception norperceivablity seem involved in our talk of their ugliness at all. Butthere does seem to be something appropriate or fitting in talking aboutimmoral beliefs as ugly and virtuous people as having beautiful souls.This appropriateness is just the sort of thing one finds w/metaphoricallanguage. So I suggest that immoral actions are only ugly in ametaphorical sense.
Now, it's also true that we characterizeand experience proofs, theories, and literary works as beautiful, andthat these judgments do not seem necessarily rooted in perception. Thesame seems true about non-perceptual imagery. But I don't think weshould assume these characterizations are metaphorical. Note that experienceis still really crucial in these cases. For example, the ordinaryjudgment that a proof is beautiful seems dependent on that proof beingthe object of someone's experience (typically your own). So too withrespect to imagery. This seems very different from the immoralbelief/action case. There it seems you might be tempted to call anaction or belief ugly just on the basis of its description. Experienceisn't required.
Upshot: I don't think the fact that wecharacterize immoral beliefs as ugly suggests that morality affectsbeauty, since I think these characterizations are metaphorical. Infact, a disturbing fact about human life and art isthat beauty and morality often pull apart in dramatic ways. Forexample, some works of art are particularly dangerous because theypresent immoral ideas beautifully. Mary Devereaux makes a nice case forthis in her paper "Beauty and Evil: the case of Leni Riefensthal's Triumph of the Will," in J. Levinson (ed.), Aesthetics and Ethics, (Cambridge: CUP, 1998).