What stands most explicitly as critique in Nietzsche’s late work in not a development from earlier interests but a return to two problems of enduring personal involvement for him, those of Wagner and of Christianity. Der Antichrist, to take one case, is not a response to a resuscitating public interest in Christian religion; it is primarily a renewed attempt to resolve for himself the question of piety.

Nietzsche ... did not settle for a demure civic conversation in the style of Richard Rorty's ironist, or saunter off with the smug nod that registers a deconstructive job neatly done. He was aware that his own criticisms and exposures owed both their motivation and their effect to the spirit of truthfulness. His aim was to see how far the values of truth could be revalued, how they might be understood in a perspective quite different from the Platonic and Christian metaphysics which had provided their principal source in the West up to now.

The primary ambition of Nietzsche’s critique of knowledge is … to demonstrate that ‘truths’ are fictions masking moral commitments.

The defects of German philosophy are those of professionalism: a closed atmosphere, books instead of life, inability to communicate discoveries to the world at large, contempt for good style, inbreeding, lack of general culture, gruesome earnestness. The defects of the cultured philosophe are those of amateurism: too many interests, superficiality, the cultivation of good style as an end in itself, the sacrifice of truth to wit, lack of intellectual honesty, philosophizing but no philosophy, inconsistency. Nietzsche achieves a balance between these two types of mind and two styles of expression: he is profound but not obscure; he aims at good style but reconciles it with good thinking; he is serious but not earnest; he is a sensitive critic of the arts and of culture but not an aesthete; he is an aphorist and epigrammist, but his aphorisms and epigrams derive from a consistent philosophy; he is the wittiest of philosophers, but he rarely succumbs to the temptation to sacrifice truth to a witty phrase; he has many interests but never loses sight of his main interests. He achieves, especially in his later works, a conciseness and limpidity notoriously rare in German writing: no modern thinker of a like profundity has had at his command so flexible an instrument of expression.

One of Nietzsche’s most important legacies to us … is his claim that it is desirable and possible to dismantle the Platonic apparatus of Forms, Absolute Truth, the Idea of the Good, etc. and its historical derivatives, such as Kant’s transcendental philosophy, and that this can be done without fear of falling into “relativism.”

Nietzsche … criticizes Schopenhauerian aesthetics for not freeing itself from Kant’s moralistic: ‘that is beautiful which gives us pleasure without interest’.

There is no important problem in any branch of philosophy which is not treated by Kant, and he never treated a problem without saying something illuminating and original about it. He was certainly wrong on many points of detail, and he may well be wrong in his fundamental principles; but, when all criticisms have been made, it seems to me that Kant’s failures are more important than most men’s successes.

The possibility of a genuine metatheory of morality is not available. Even psychology has its ethical presuppositions. … A metatheory of morality would be legitimate only if the existence of a hierarchy of absolute, and hence unconditioned, truths were established. They would then provide a framework of supra-ethical categories. The primary ambition of Nietzsche’s critique of knowledge is to expose just such an exercise … as sleight of hand, an efficacious deception. This critique sets out to demonstrate that ‘truths’ are fictions masking moral commitments

With these dramatic words, Kant alludes to the two great problems and accomplishments of his philosophical career. On the one hand, he wants to know how we who as creatures are a mere part of nature can discover how all of nature … does and even must work. On the other hand, he wants to display the unconditional value that we have as rational rather than merely natural beings, … and that we are always free to act in accordance with and indeed for the sake of this principle, thus free to realize the unconditional value for which we unlike anything else in nature have the potential.

For it is only in the Critique that all the various strands of Kant's thought are woven together into the pattern of his practical philosophy. This pattern, in turn, can be understood only in the entire fabric of the critical philosophy, and that rich design can be clear only to those who have understood each of its three principal parts, which are the three Critiques and not shorter and more popular works like the Prolegomena and the Foundations.

This is Nietzsche’s twofold struggle: against those who remove values from criticism, contenting themselves with producing inventories of existing values or with criticizing things in the name of established values (the “philosophical labourers”, Kant and Schopenhauer, BGE 211); but also against those who criticise or respect values by deriving them from simple facts, from so-called “objective facts” (the utilitarians, the “scholars”, BGE Part 6). In both cases philosophy moves in the indifferent element of the valuable in itself or the valuable for all. Nietzsche attacks both the “high” idea of foundation which leaves values indifferent to their origin and the idea of simple causal derivation or smooth beginning which suggests an indifferent origin for values. Nietzsche substitutes the pathos of difference or distance (the differential element) for both the Kantian principle of universality and the principle of resemblance dear to the utilitarians. “It was from the height of this pathos of distance that they first seized the right to create values and to coin names for them; what did utility matter?” (GM I 2 p. 26)

Nietzsche's problem is how to be a philosopher once he has grasped the finitude of philosophy.

For Kant, analogy was the wellspring of all creativity, and Nietzsche gave a famous definition of truth as “a mobile army of metaphors”.

Nietzsche himself was a great moralist; his writings abound with value judgments about individuals, character types, modes of thinking, and national traits. It is as if he develops immoralist psychology in order to tame his own nature, to keep his own greatest vice in check.