In philosophy since Descartes and Bacon, and especially since Locke and Hume, the underlying goal has been to extricate thought from metaphysics—or, to use a more loaded term, "superstition." The dream of Descartes one November night in 1619 was the achievement of a single body of verified knowledge in every area of human endeavor. And the obvious way to such a body of knowledge was to be a method that set up criteria for achieving it. Hume, then Kant, then Nietzsche took up the fight against "metaphysics." Kant, as Foucault has noted, preserved the autonomy and freedom of man only by making him an "empirical-transcendental doublet,"¹⁸ thus escaping the depressing metaphysical consequences of Hume's radical empiricism. Yet this solution only substituted the metaphysical presuppositions of German idealism for the metaphysics of the great rationalists—Descartes, Spinoza, Leibniz, and Wolff.

It is Nietzsche, the relentless iconoclast, who goes to the roots of modern thought and who, in my opinion, is philosophically the door to postmodernity a door entered by Heidegger with results more radical than Nietzsche himself would have dreamed.¹⁹ Nietzsche attacked Descartes, Kant, Schopenhauer, Christianity (as a life-denying form of Platonism-for-the-masses), scientific objectivity, romanticism, Wagner, morality, contemporary art, Germans, and so on. When Nietzsche was through "philosophizing with a hammer," the thought-forms on which the nineteenth century lived were in pieces. Nietzsche's thought was a conflagration, a purification of modern thought, and a careful study of his work is radical therapy for many illusions in twentieth-century thought.

Nietzsche passionately hated his own time, which he identified with the untragic this-worldliness of the Greek Alexandrian age. The modern age, he argued, lives on the lethal legacy of Socratic thinking—grounded in abstractions and theories, and willing to die for truths produced by rational deduction. Modernity, as Nietzsche saw it, is a combination of Alexandrian this-worldly trivality and Socratic absurd logocentrism. Nietzsche attacked the metaphysical view that man is a "thinking thing" or some kind of mental substance lodged in inert matter. This Cartesian dualism creates the "mind-body problem" and a view of man as a "ghost in a machine" (to use Gilbert Ryle's famous phrase from Concept of Mind). Nietzsche questioned whether what we call "consciousness" is truly the seat and core of subjectivity; rather, he suggested that in each human being a plurality of interpretative principles or centers (Herrschaftszentren)), like medieval fiefdoms, are in tension and competition with each other. Waking consciousness is only one of these centers, and perhaps a monitor of things rather than king of them all. He resolutely denied every metaphysical order of reality—that is, any order of reality above and outside the phenomenal world in which we have our experience. Such a belief, he held, was merely a form of Platonism. No firm and enduring "reality" lies behind the phenomenal world—no Hinterwelt.

For Nietzsche, human knowledge does not represent a contact with a "truth" behind phenomena; rather, it is a function of our life-goals. As Habermas has articulated it in the present decade, knowledge is "interest-guided."

Objective, scientific knowledge does not give us the form of the "way things are"; it is fabricated by the artistry of understanding in conformity with the purpose of gaining control over nature. If our interest or aim were different, our knowledge would take another form. Habermas, for instance, distinguishes the knowledge-guiding interests of the empirical-analytic sciences (a technical-cognitive interest) from the historical-hermeneutic sciences (a practical and action-orienting interest), both of which differ from the "critical sciences," which are neither technical nor pragmatic but emancipatory. Psychoanalysis is an example of the latter and is for Habermas the model of emancipatory reflection. Habermas attaches a special importance to emancipatory reflection for through its reflexivity man liberates himself from illusions. The knowledge gained from emancipatory reflection, unlike the other forms of knowledge, is worthless unless the subject himself is liberated through it. In its philosophical form, "critical theory" has the function of turning reflection back on the agent. Habermas holds that for this reason it goes beyond merely "hermeneutical" reflection to a form of thought that frees man from the internal and external chains of ideology.²⁰

We could say, then, that Nietzsche, and after him, Habermas (as well as Marx and Freud) show the ideological character of human knowledge, shattering the firm underpinnings for knowledge as something grounded in immutable principles or transcendental categories. Thus, Nietzsche went beyond an attack on metaphysics to argue that knowledge itself, as the artistry of an interestguided understanding, cannot be "truth" in the old rationalist sense. There are only different forms of "fiction." What we call "truths," said Nietzsche, are merely the useful "fictions" by which we live.²¹