Kant's invention of the metaphor

In the Critique of Pure Reason, Kant notices that the only way reason can hope to fulfill the completeness it seeks for, besides in a constitutive way, is to employ reason regulatively: to proceed in the employment of reason 'as if' there is unity or purpose or completeness in this world. At first glance, this solution seems a little ridiculous. And it is, if one understands this philosophy of the 'as if' narrowly, to be performing a designated technical function of creating illusions about things which are not really there for reason's apprehension. Indeed, this is precisely the function Kant requires of it. But at the same time, setting aside the actual job of the 'as if' in Kant's system, I note that Kant discovers the metaphor by discovering the as if: as if he is saying, "completeness" but not literally, but metaphorically. He thus interprets the metaphorical use of reason as its central and definitive employment, and therefore puts the "scare quotes" around completeness. It is, a "so to speak" completeness - a "so to speak" philosophy.
And this is no mean achievement, for by doing this, Kant recaptures the very gesture of philosophy: philosophy as solipsistic self-stimulation, as speculation (as Hegel reads it), or (as Schopenhauer reads it) atheism and non-meaning (if by meaning we mean something literal), or as a tragic abysmal view of life that sees no secure ground to stand on, as the non-belief in the grammar and logic of language, as the free license to express even the minutest thought and experience as hiding a wealth of debris (the last three as Nietzsche views it), or the play of interpretations (Gadamer/Derrida), or as the concern with art, beauty, imagination and free-play that tip-toes above all the seriousness and gravity of analytic salvation-seekers (as the entire post-structuralist movement). Kant's metaphor reveals the complete lack of a language that philosophy can call its own, that it had been parasitic on a scientific language that has now claimed its independence. In short, Kant's invention of the metaphor shows the inevitable truth: the flickering existence of philosophy, which nevertheless refuses to extinguish itself.