The best way to think about the human task of living is that it should be, as Nietzsche said, a continual journey of self-overcoming. The project should be that embodied in the great religions’ concepts of salvation or nirvana: to overcome particularity, to wash out the blemishes of self-fixated particularity. That is, to fuse the particular, i.e. oneself, with the universal, by remaking oneself in its light. We are born spotted, tainted with the “sin” of self-immersion, base impulses, and ignorance; our task is to become (relatively) spotless, elevated above ordinary determinations so that in freedom we master ourselves. The imperative, in short—the categorical imperative—is to be clean, and, on the whole, whatever doesn’t make you feel clean should usually be rejected as ignoble and corrupting. We all have capacities for high and low things, for things that a universal humanity would appreciate and things it would despise. Our calling is to cultivate the former capacities and let the others atrophy. –On one side is stupidity, ignorance, slavishness, unreasoned emotion, unconcern for others, greed, smugness, hedonism, and brute bodily pleasures, all things that entrap within the determined self, the unfree and “unclean” self ruled by animal impulses. On the other side is intelligence, knowledge, courage, reason, compassion, generosity, a deep humility, and “spiritual pleasures,” things that liberate from the self’s primal immediacy and so make free and dignified. Insofar as these latter qualities are grounded in internalization of “the other’s” perspective—broadening of experience and the desire to impress the other—which is a uniquely human capacity that makes possible our very self-consciousness, they are, in a sense, the fulfillment of human potential, of the universality implicit in self-consciousness. The former qualities, by contrast, are merely human manifestations of the lowest animal conditions and instincts. Stupidity, for example, is utterly immersed in itself; intelligence incorporates others.
While it may sound odd, therefore, the idea of cleanliness—moral, intellectual, emotional, aesthetic, etc.—is a useful “regulative principle” for human thought and action (to speak in Kantian language). It is evocative; it is imprecise but elevating, and recalls that other ennobling idea, the concept of universality. It shouldn’t be confused with purity, which is extreme, potentially fanatical and anti-humanistic; cleanliness is more moderate—merely moral, beautiful, rational, humane, elevated above petty resentment and neurotic fixations. One can also use the idea of cleanliness as a test to determine what is “decadent”: if some cultural artifact doesn’t seem healthy, a sign and product of good health, vigor, or lofty universality, one might well call it decadent—that is, a symptom of sickness, neurasthenic self-consciousness, polluted and anti-human life, pathological social atomization, or psychological and cultural exhaustion. Most twentieth-century avant-garde art is decidedly decadent (which doesn’t mean it’s worthless). Even late-nineteenth-century composers, such as Brahms and Wagner, can be very decadent, unlike Mozart and Haydn. The social context of the former was, so to speak, dirty and sick (hypochondriacal, navel-gazing)—as you can sometimes hear in its music—that of the latter relatively clean and vital, naïvely confident.
The ideals of cleanliness and universality overlap with, but are superior to, Nietzsche’s ideals of strength, enthusiasm, “overflowing vitality,” instinct, virtù in the Renaissance sense. There is some intuitive plausibility to Nietzsche’s judging the worth of things by determining where to place them on the spectrum from shriveled weakness to brimming-over strength. This standard of value is reminiscent of past “aesthetic moralities” that center not on the antithesis right/wrong or good/evil but on noble/base: Aristotle’s ethic of virtue is an example, as is, perhaps, Goethe’s (unoriginal) conception of the “genius” whose demonic vitality is such that he isn’t bound by ordinary standards of right and wrong. One problem with such an emphasis on “strength,” of course, is that it subordinates the claims of altruism to those of egoism. The weak but good man is considered lower than the strong but amoral man. Another problem is the vagueness of words like “strong” and “weak”: their meanings are elusive, tending to evaporate the more closely you examine them. Moreover, insofar as the terms are meaningful at all, someone can be psychologically strong and weak in different respects—indeed, everyone is both strong and weak (whatever that means). A third problem, perhaps most damning, is that the Nietzschean—or Calliclean—value-system is the parochial ethic of the master class, which has the requisite leisure and privilege to care about individualistic values of “virtù” and whatnot. To people preoccupied with the tasks of survival, all this master-moralizing seems juvenile, parasitic, self-indulgent, a mere luxury. It’s unreal. What makes more sense is to try to be morally and intellectually clean—compassionate, cooperative, communally oriented, not self-fixated but attuned to the health of the collective, which is also the health of the self. One attains a kind of universality—and “strength”—simply by working together with others, molding and being molded by them, internalizing their perspectives, thus achieving intelligence, knowledge, courage, reason, and the other noble values that thinkers from Plato to Nietzsche have upheld (in different ways and for different reasons). The egoistic ideal of strength or “health” is therefore best achieved precisely through altruism, which can also be a symptom of it.
 Goethe’s example is Napoleon. In Dostoyevsky’s Crime and Punishment, Raskolnikov is initially seduced by this ethic, until through suffering he rises to the higher Christian morality. It’s worth noting, by the way, that the Nietzschean and Goethean standards of value were already recognized, and rejected, by Plato, whose character Callicles espoused them in The Gorgias.