I desire that your conjectures should be limited by what is thinkable. Could you think a god? But this is what the will to truth should mean to you: that everything be changed into what is thinkable for man, visible for man, feelable by man. (Nietzsche, Thus Spoke Zarathustra)

Nietzsche would reduce everything to “what is thinkable for man” and then show that “what is thinkable for man” — self-destructs, falls through itself, utterly collapses like a black hole into….nothing. Hence nihilism and through nihilism and only through nihilism: INCIPIT ZARATHUSTRA!¹

Supposing there were no self-identical “A”, such as is presupposed by every proposition of logic (and of mathematics), and the “A” were already mere appearance, then logic would have a merely apparent world as its condition. In fact, we believe in this proposition under the influence of ceaseless experience which seems continually to confirm it. The “thing”— that is the real substratum of “A”; our belief in things is the precondition of our belief in logic. The “A” of logic is, like the atom, a reconstruction of the thing — If we do not grasp this, but make of logic a criterion of true being, we are on the way to positing as realities all those hypostases: substance, attribute, object, subject, action, etc.; that is, to conceiving a metaphysical world, that is, a “real world” — this, however, is the apparent world² once more… (Nietzsche, Will to Power)

In his 2013 essay, ‘Three Forms of Meaning and the Management of Complexity’³, Jordan Peterson repeatedly registers his attachment to the fabled ‘thing in itself’ and does so through what Nietzsche calls “our belief in things”. But Peterson begins his essay by setting out a preliminary overview of perception⁴ which would seem to rule out any such access:

Most psychological models (…) are based on the assumption that the world is made of objects, existing independently and given — or, more abstractly, of stimuli. That assumption is incorrect: the boundaries between objects or stimuli are largely situation-dependent and subjectively-determined. Half our brain is devoted to vision. This indicates that we do not simply see what is there. The “frame problem”⁵ (…) looms over all other current psychological concerns. We live in a sea of complexity. The boundaries of the objects we manipulate are not simply given by those objects. Every object or situation can be perceived, in an infinite number of ways, and each action or event has an infinite number of potential consequences.⁶

• The boundaries between objects or stimuli⁷ are (…) subjectively-determined
• we do not simply see what is there
• objects (…) are not simply given
• Every object or situation can be perceived in an infinite (or, at least, indefinite) number of ways

Still, Peterson is somehow able to stipulate how things are with the thing-in-itself, indeed with “all things-in-themselves”: 

Intelligible arrays have been identified at many levels of resolution: from that of the quark, 1/10,000² as large as an atom, to the supra-galactic, at 10²⁵ meters. All things-in-themselves exist simultaneously at all those levels, and partake in multiple arrays, at each level. A perceptible object is thus an array segregated, arbitrarily and for subjective purposeful reasons, from its participation in endless other arrays. However, some aspect of the original array [the original array!] must be retained. Otherwise, the object cannot be said to truly exist, and must be regarded as fantasy. (…) The perceived object is simpler than the thing-in-itself (a prerequisite to comprehension) -– while remaining importantly related⁸ to the actual thing.⁹ (…) The perceived object is thus a low-resolution image of the thing-in-itself.¹⁰

Compare Nietzsche (from a late note included in the posthumously assembled Will to Power):

Radical nihilism is (…) the realization that we lack the least right to posit a beyond or an in-itself of things.

Nietzsche agreed with Peterson that absent certain presuppositions (aka, needs) “the object cannot be said to truly exist”. But exactly contrary to Peterson, Nietzsche denied those presuppositions and even those needs. All was indeed a “fantasy” — except that, absent subject and object, “fantasy”, too, must be dispensed with as self-cancelling => fantasy.

A footnote in Peterson’s essay continues his stipulation that the thing-in-itself is available for our manipulation:¹¹

What is axiomatic about the object is that it is a representation of the thing-in-itself, sufficient for some delimited purpose.¹²

Given this stipulated axiom, as Peterson claims in the same place, “the object is less than the thing-in-itself and (…) can [yet] still be empirically ‘real’.”¹³ The enabling assumptions here are that the thing-in-itself and reality are coterminous and that the thing-in-itself can somehow lend that reality to a representation of it in and as a perceived object. Hence, the thing-in-itself is real and its object, while at an unaccountable psychological remove from it, is also ‘real’. 

Now Nietzsche took the same view as Peterson that the thing-in-itself and reality are coterminous. But he concluded, since we lack any access to the thing-in-itself, that we must do also without that “esteemed commodity”¹⁴ of “reality”. He set out the history of the dissolution of our access to reality in a famous aphorism from Twilight of the Idols:

How The “True World” Finally Became A Fable: The History of an Error

1. The true world — attainable for the sage, the pious, the virtuous man; he lives in it, he is it.  (The oldest form of the idea, relatively sensible, simple, and persuasive. A circumlocution for the sentence, “I, Plato, am the truth.”)
2. The true world — unattainable for now, but promised for the sage, the pious, the virtuous man (“for the sinner who repents”).  (Progress of the idea: it becomes more subtle, insidious, incomprehensible — it becomes female, it becomes Christian. )
3. The true world — unattainable, indemonstrable, unpromisable; but the very thought of it — a consolation, an obligation, an imperative.
(At bottom, the old sun, but seen through mist and skepticism. The idea has become elusive, pale, Nordic, Königsbergian [ie, Kantian].)
4. The true world — unattainable? At any rate, unattained. And being unattained, also unknown. Consequently, not consoling, redeeming, or obligating: how could something unknown obligate us?  (Gray morning. The first yawn of reason. The cockcrow of positivism.)
5. The “true” world — an idea which is no longer good for anything, not even obligating — an idea which has become useless and superfluous — consequently, a refuted idea: let us abolish it! (Bright day; breakfast; return of bon sens and cheerfulness; Plato’s embarrassed blush; pandemonium of all free spirits.)
 6. The true world — we have abolished. What world has remained? The apparent one perhaps? But no! With the true world we have also abolished the apparent one. (Noon; moment of the briefest shadow; end of the longest error; high point of humanity; INCIPIT ZARATHUSTRA.)

Peterson has written and lectured on Nietzsche a great deal, including on Zarathustra. But his heroic reading has not taken that step beyond “the thing-in-itself”, “beyond good and evil” (another of Nietzsche’s books often discussed by Peterson), where Zarathustra — starts!

Point #6 is (or, at least, should be) of critical importance for Peterson. For not only is it not the case that we have some sort of inexplicable access to the thing-in-itself, we also have no access to the apparent world — exactly because we lack of access to the thing-in-itself. The apparent world, including our apparent selves, is, unfortunately, sadly enough, along with the real world and our real selves — missing.

Stipulation of any access to the real or even the apparent world is dependent on some ground (hence Peterson’s various appeals to the thing-in-itself, or to brain materialism¹⁵, or to the hero’s penetration to “the constituent elements of experience”¹⁶ and, throughout his work, to uralt mythology¹⁷). But none of these stipulations can succeed, for reasons that Nietzsche already made clear 150 years ago, since all remain, in Peterson’s words, “mere arbitrary supposition”.¹⁸ 

What has happened is that Peterson has made the human, all-too-human error of mistaking the strange threshold of the way we need to go — for an endpoint. It is, he thinks, a problem to be solved through the stipulation of some ground. Or waved at as an eternally ventured and eternally indistinct heroic quest. In any case, he has refused in various ways the labyrinthine path to Zarathustra’s incipit. 

The central demand at this threshold is that “the constituent elements of experience” be identified — as indeed Peterson knows.¹⁹ But the hero cannot know “the constituent elements of experience” absent the possibility of doing so. That is, before he can know “the constituent elements of experience” the hero must have visited “the constituent elements of experience” and activated or “put on” (as McLuhan would say) that one of them, or that one combination of them perhaps, through which knowledge of “the constituent elements of experience” is first of all possible. Unfortunately the hero cannot accomplish this somersault in time without losing himself in the process. Only the ‘nobody’ can follow Zarathustra into that ‘convalescence‘ which is so desperately needed by the world.