[Topics: Critical Idealism, Empiricism, Metaphysics, Rationalism]
Controlled Demolition:

How Immanuel Kant Rescued the Field of Metaphysics by Tearing it Down


Immanuel Kant Sketch by M.R.P. - metaphysics

Caricature Sketch by M.R.P.


In popular discourse, the word ‘metaphysics’ is used derisively to refer to baseless mysticism. But that’s not how philosophers use the word. In philosophy, metaphysics stands alongside topics like epistemology, ethics, and logic as a major branch of the field. Put simply, for philosophers, the word ‘metaphysics’ refers to the field that concerns itself with the nature of being. Accordingly, this field asks extremely fundamental questions, like: At the lowest level, what is there in reality? What constitutes the identity of a singular thing? And how and when does one thing ever become a different thing?

Given such important and fundamental subject matter, it may surprise you to hear Immanuel Kant’s account of the state of metaphysics toward the end of the Enlightenment: “All false art, all vain wisdom, lasts its time but finally destroys itself, and its highest culture is also the epoch of its decay. That this time is come for metaphysics appears from the state into which it has fallen among all learned nations” (Kant Prolegomena 998).

In these words, and others like them, Kant mounts an attack on the metaphysical philosophy of both his contemporaries and of the centuries leading up to his lifetime. He felt that the field amounted to little more than a highly formalized version of what the word ‘metaphysics’ conjures among laypeople today: baseless mysticism. It was baseless, he felt, because it amounted to nothing but coherent guesswork (i.e. as long as folks kept their systems consistent, they were entirely unfalsifiable); and it was mystical, he felt, because it was completely disconnected from the actual grounds of all knowledge (i.e. it was not pertinent to our actual experiences in life, our possible experiences in life, nor the conditions that make experience in general possible).

But despite these glaring flaws he identified, Kant felt the field was not entirely beyond salvaging, and he himself made a concerted effort toward clearing away the centuries of mistakes in order to provide a new and firm ground from which to build anew.

Plato Sculpture after Silanion, Photo by Marie-Lan Nguyen - Immanuel Kant, metaphysics

Plato (copy of sculpture by Silanion)
Photo by Marie-Lan Nguyen

What Immanuel Kant Argues We Can’t Know:

Kant’s intervention in this aspect of philosophy could be summed up as him saying: ‘Look, folks have been trying to make progress in the field of metaphysics for millennia in a haphazard way. They’ve allowed reason to cook up its own intellectual systems entirely distinct from experience, or have extrapolated wildly from experience. In doing that, they’ve created all kinds of totally unverifiable ideas—such as Platonic forms, specific conceptions of God, and immortal immaterial souls—and have also engaged in various wrongheaded debates—such as whether there is causal free will in reality, or whether reality (not the universe, mind you, but reality) is infinite in regards to time and space. Such philosophers, though starting from the world or from their understanding, have strayed far beyond the bounds of all possible experience.’

That, to him, is a big mistake. Brilliant people, Kant contends, have wasted untold hours and effort in the creation and discussion of such apparently coherent metaphysical ideas—all of which were created without first establishing how or if it would be possible to distinguish truth from falsehood in metaphysics, and hence none of which can be said to have actually expanded our knowledge in any real way. So, he writes, with biting criticism: “We may blunder in various ways in metaphysics without any fear of being detected in falsehood. For we never can be refuted by experience if we but avoid self-contradiction.” (Kant Prolegomena 982)

And further:

[. . .] there are doubtless many who, like myself, have not been able to find in all the fine things that have for long past been written in this department anything that has advanced the science by so much as a finger’s breadth. We find indeed the giving a new point to definitions, the supplying of lame proofs with new crutches, the adding to the crazy-quilt of metaphysics fresh patches or changing its pattern; but all this is not what the world requires. The world is tired of metaphysical assertions; what is wanted is the possibility of this science, the sources from which certainty therein can be derived, and certain criteria by which it may distinguish the dialectical illusion of pure reason from truth. (Kant Prolegomena 1004)

But that doesn’t mean that metaphysics, as a practice of seeking new knowledge with reason, apart from experience, a priori, is entirely impossible. We don’t only want “the possibility of this science,” but can actually get there.

In fact, Kant argues, we already know it can be done: we create new knowledge apart from experience when we do pure mathematics; and we do it, more controversially, when we generate or generalize scientific laws of nature. So, surely, we can do it for philosophical topics as well. But we will have to first take a big step back, and get clear on how exactly we get to know such things, and in general get to know anything about the world.

Upon taking that big step back, Kant’s most important innovation (which is also the reason he referred to his work as bringing about the equivalent of the Copernican revolution for the field of philosophy) is his incredibly clever and perceptive argument that what accounts for people having been so frequently tempted into extensive metaphysical guesswork—is that they have erroneously assumed that they have (or can gain) access to the world as it is in itself, apart from human cognition:

Up to now it has been assumed that all our cognition must conform to the objects; but all attempts to find out something about them a priori through concepts that would extend our cognition have, on this presupposition, come to nothing. Hence let us once try whether we do not get farther with the problems of metaphysics by assuming that the objects must conform to our cognition [. . .] (Kant Critique 110, Bxvi)

In my opinion, a fruitful way of beginning to understand this position is to tentatively think of Kant as a negative epistemologist. And by this, I do not mean as a pessimistic epistemologist. What I mean is that he is a philosopher with valuable insights into what we can’t know, at least as much as what we can.

Think about the fact that you have no way of accessing sight other than your faculty for visual perception, no way of accessing sound other than your faculty for auditory perception, and no way to think about the world other than your own understanding and reasoning faculties. Your set of outer and inner senses can in this context be understood as offering not only the ability to have experience, but also the limitations or bounds to your experience. The world as it is represented by your senses and your understanding is the only world you’ll ever know.

A human can’t access the world in any way whatsoever without using human cognition to do it. The only way in which we know a world at all, and ourselves within it, is through the way that it and we are represented to us by our sensing faculties—our understanding faculty then categorizes and unifies those representations into our experience of the world, and our reasoning faculty thinks about it. People can’t generate true knowledge that is entirely distinct from experience because everything they know is either actual experience, possible experience, or a form or faculty that makes experience in general possible.

In light of these clarifications, the error Kant is highlighting in the metaphysics of earlier philosophers can be forcefully brought out by phrasing the objection like this: most philosophers have implicitly or explicitly believed that they could gain certainty about what is beyond the realm of human cognition by exclusively using human cognition.

So, if we’re to save metaphysics, then the questions and goals of the field must in some sense be brought back into the same zone as its methods, back into the area we can actually access—within the realm of human cognition.

But wait: didn’t I say a few paragraphs ago that Kant believes we can “create new knowledge apart from experience?” Yes, absolutely. But there’s no contradiction there. The key is that such knowledge, even if generated apart from experience, can not be entirely distinct from experience; it must pertain to experience. All of what Kant would consider to be our genuine metaphysical knowledge holds true only with regard to experience. It must relate to either actual experience in life, possible experience in life, or the conditions for the possibility of experience.

What Immanuel Kant Argues We Can Know:

When it comes to some of our most basic apparent cognitive constraints, Kant is fond of pointing out that all objects that appear to us, appear in time and space. Time and space, then, are apparently necessary forms of our intuition. This is a great example of what he means by saying “the objects must conform to our cognition”—that we will only ever understand things by representing them with extension and separation (space), and thinking about them in some succession (time). But is anything, as is it in itself, apart from our cognition of it, truly in time and space as we understand those concepts? For a few different reasons, Kant says it is not; but I think the more accurate response to that question from the overall standpoint he’s describing would be to say that we simply do not know.

David Hume by Allan Ramsay - Immanuel Kant, metaphysics

David Hume by Allan Ramsay

Regardless, please notice: Kant isn’t saying time and space aren’t real, or that we change them with our thoughts and feelings. A pet peeve of mine is when people try to introduce Kant to students by talking about how time seems to speed up when a person is enjoying themselves, and slow down when they aren’t. Kant doesn’t care much about those kinds of emotional experiences that people have. On the contrary, what Kant is talking about comes in before any thinking or reasoning or reacting, emotional or otherwise, can occur. He’s actually just pointing out that when you consider how the world appears to us, how it is represented to us by our sensing faculties, a couple really fundamental attributes of that appearance or representation would be space and time. Things only ever appear to us in space and time, as though those are the only ways or forms through which we are able to represent the world.

With this example in mind, we are ready to ditch the tentative description of Kant as a ‘negative epistemologist’ from the previous section, and turn to his ‘positive epistemology,’ which is to say his work on what we can know. Hence the following account from Paul Guyer and Allen Wood’s introduction to the Cambridge edition of the Critique of Pure Reason:

[. . .] while he attempted to criticize and limit the scope of traditional metaphysics, Kant also sought to defend against empiricists its underlying claim of the possibility of universal and necessary knowledge

[. . .]

Kant’s position thus required him not only to undermine the arguments of traditional metaphysics but also to put in their place a scientific metaphysics of his own, which established what can be known a priori but also limits it to that which is required for ordinary experience and its extension into natural science. (Kant Critique 2-3)

So, if all we know or can know must pertain to experience, then metaphysics can be salvaged and reinvented . . . by making it a study of the conditions for the possibility of experience. This would be a study of how sensations and understanding come together to make experience, and what reason is capable of doing with that experience (the notion that time and space are forms of our intuition would be a prominent example of the fruits of such a study).

This new and valid metaphysics must turn our attention to how subjects take in, unify, and categorize information. We aren’t necessarily using information from experience to generate this knowledge; we are genuinely creating or discovering new knowledge with reason alone, just like folks always wanted to. It’s just that the knowledge in question will always pertain either to some possible experience or to what makes experience possible in general. It is in this spirit that Kant frames his presentation of these ideas as a “Critique” of pure reason, by which he means an exhaustive study of the structures, abilities, and limitations of pure reason. To accomplish that, he ends up providing his entire conception of human cognition: sensibility, understanding, and reason.

But armed with this new approach, Kant is ready to face down two very different sets of opponents. On the one hand, he rejects the dogma of the rationalists—that pure reason, considering matters entirely disconnected from our actual and possible experiences in every way, can beget true knowledge:

The outcome of all dialectical attempts of pure reason not only confirm [. . .] that all the inferences that would carry us out beyond the field of possible experience are deceptive and groundless, but it also simultaneously teaches us [. . .] that human reason has a natural propensity to overstep all these boundaries, and that transcendental ideas [. . .] effect a mere, but irresistible, illusion, deception by which one can hardly resist even through the most acute criticism. (Kant Critique 590, A642/B670)

And on the other hand, he rejects the skepticism of the later empiricists—that most or all purportedly universal and objective knowledge is actually illusory. In particular, he has in mind David Hume’s claim that the concept of causation is not universal, nor objective, nor even strictly logical, as it is in fact nothing more than a kind of mental habit formed after repeated experience. Kant responds that causality, and some similarly fundamental concepts which Humean skepticism could be extended to doubt, are universal and objective with regard to the phenomenal world—because they are not a posteriori inventions or discoveries, but rather pure concepts of the understanding, which is to say notions that our understanding faculty has innately and uses a priori to construct our experience of the world (i.e. to construct the world as it appears to us):

I am very far from holding these concepts to be derived merely from experience, and the necessity represented in them to be fictitious and a mere illusion produced in us by long habit. On the contrary, I have amply shown that they and the principles derived from them are firmly established a priori before all experience and have their undoubted objective rightness, though only with regard to experience.

[. . .]

This complete (though to its originator unexpected) solution of Hume’s problem rescues for the pure concepts of the understanding their a priori origin and for the universal laws of nature their validity as laws of the understanding, yet in such a way as to limit their use to experience, because their possibility depends solely on the reference of the understanding to experience, but with a completely reversed mode of connection which never occurred to Hume: they are not derived from experience, but experience is derived from them. (Kant Prolegomena 965-6)

Interestingly, although Kant’s efforts at restructuring metaphysics (and the accompanying ethical system he developed in the ensuing decades) are what he’s most known for . . . that really only accounts for part of his initial aim. Another part was not to save metaphysics, but to save science. Notice: if Hume’s skepticism of causation and induction goes undefeated, then natural science is reduced to an ultimately unfounded body of habitual guesswork and belief. So Kant wanted to provide, as he says there, “for the universal laws of nature their validity as laws of the understanding.” He does this by arguing, first, that causation is not a concept learned from the world but instead one of the ways that cognition constructs the world as it appears to us, and, second, that scientific law actually refers to the consistent, universal operation of such cognition.

So, Kant basically offers a middle way or compromise between rationalism and empiricism. He rescues from Hume’s skeptical clutches not only scientific causality but several related fundamental concepts, maintaining (like a rationalist) that they are objective, innate, and universal—and yet does so without losing sight of the primal necessity and relevance of experience for all forms of knowledge, even metaphysical knowledge (like an empiricist).


Immanuel Kant saw plainly that, in his time, the field of metaphysics was like a house made of twigs—by no means a useful or respectable structure, and vulnerable to being tipped over by a stout breeze. So he filled up his lungs and blew it down. But he was no mere critic; Kant toppled metaphysics in order to rebuild it, on a proper foundation:

That the human spirit will ever give up metaphysical researches is as little to be expected as that we should prefer to give up breathing altogether, in order to avoid inhaling impure air. There will, therefore, always be metaphysics in the world; nay, everyone, especially every reflective man, will have it and, for want of a recognised standard, will shape it for himself after his own pattern. What has hitherto been called metaphysics cannot satisfy any critical mind, but to forego it entirely is impossible; therefore a critique of pure reason itself must now be attempted or, if one exists, investigated and brought to the full test, because there is no other means of supplying this pressing want which is something more than mere thirst for knowledge. (Kant Prolegomena 998)

The firm basis on which Kant endeavored to rebuild metaphysics, allowing it to be both a science itself and compatible with natural science, could be called either ‘cognition’ or ‘experience.’ But the argument, the study, the “critique”—that leads to that being the basis is a complex and subtle one, which I have attempted to lightly introduce in this article. In the course of his argumentation, Kant lays out an entirely new way of discussing the world, which he initially named ‘transcendental idealism.’ This is his doctrine that (1) all objects we encounter in the world must conform to our cognition; (2) the cognition in question constructs our experiences, and is composed of our sensibility, our understanding, and our reason; and (3) we have no access whatsoever to the world as it is in itself, apart from our cognition of it.

By ‘transcendental’ Kant means, basically, ‘prior to and underlying experience.’ This is contrasted with the idea of the ‘transcendent,’ which would mean, basically, ‘above and beyond experience.’ As for ‘idealism,’ Kant means to say that his system pertains to that which is transcendental about the mind—the way that cognition works to create experience.

He later declared that it would be more appropriate to call his system ‘critical idealism,’ to make it clear that it radically differs from other types of idealism. But it wasn’t really the word ‘transcendental’ that was causing big issues for folks understanding it; it was the word ‘idealism’ that his contemporaries were getting stuck on. Because Kant used the word ‘idealism’ in naming his system, many folks assumed that he was saying only the world of appearances exists, and that the world itself, apart from human cognition of it, is an illusion. But that’s not his point at all. He argues that something must really underlie the appearances, though by definition we only ever perceive the appearances. His actual point is simply that we can’t access anything without it being filtered through our cognitive apparatus, and that allowing our reasoning faculty to believe it can is a big mistake.

Or, as Kant clarifies (while slightly misrepresenting the work of Berkeley),

The dictum of all genuine idealists, from the Eleatic school to Bishop Berkeley, is contained in this formula: “All cognition through the senses and experience is nothing but sheer illusion, and only in the ideas of the pure understanding and reason is there truth.”

The principle that throughout dominates and determines my idealism is, on the contrary: “All cognition of things merely from pure understanding or pure reason is nothing but sheer illusion, and only in experience is there truth.” (Kant Prolegomena 1002)

Taken altogether, the propositions of transcendental or critical idealism imply that if we wish to speak of something which we can actually access, about which we can actually have knowledge, then it will have to pertain to our experience of the world—have to pertain to the world as it conforms to our cognition. This means that all that we can know a priori, independent of experience, is how cognition processes the inputs of the senses to construct, unify, and consider experience. So if there is ever to be a legitimate field of metaphysics, that must be its domain.

Works Cited:

Kant, Immanuel. Critique of Pure Reason. 1781. Translated by Paul Guyer and Allen W. Wood. Cambridge University Press, 1998. Print.

Kant, Immanuel. Prolegomena to Any Future Metaphysics. 1783. Classics of Western Philosophy. Translated by Paul Carus and James W. Ellington. Edited by Steven M. Cahn. Hackett, 1990, pg. 933-1008. Print.

[Topics: Critical Idealism, Empiricism, Metaphysics, Rationalism]
Controlled Demolition:

How Immanuel Kant Rescued the Field of Metaphysics by Tearing it Down

was last modified: February 3rd, 2024 by Daniel Podgorski
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