As far as I know, Immanuel Kant (1724-1804) believed that space and time do not exist objectively, independent of us, and that they are added by our minds to our perceptions. I am eager to know what his argument/justification was for this claim. Later, Arthur Schopenhauer (1788-1860) accepted this, and argued that multiplicity and plurality are only apparent, the reality is one single entity, because, he said, to distinguish things, time and space are required – two things can be differentiated only if they occur at different times or places.

  • You may find this an opening
    – Rushi
    Commented Oct 22, 2019 at 7:18

3 Answers 3


There's a lot going on in the body of your question, but I'm only going to address the Kant part.

Kant's position is subtly different than what you are claiming. For a thorough discussion, see the SEP article on Kant's view on time and space.

I'm primarily just going to work from that and try to simplify it with reference to precisely what you are claiming and asking. Let's start, however, by distinguishing two things:

  1. The claim that time and space do not exist objectively.
  2. The claim that I have no objective unfiltered access to time and space.

On my reading, Kant is committed to something close to 2 but not to 1. 1 is a claim about what isn't "out there." 2 is a claim about the way minds work.

Thus, Kant states

Space is not an empirical concept which has been derived from outer experiences. For in order that certain sensations be referred to something outside me (that is, to something in another region of space from that in which I find myself), and similarly in order that I may be able to represent them as outside and alongside one another, and accordingly as not only different but as in different places, the representation of space must already underlie them [dazu muß die Vorstellung des Raumes schon zum Grunde liegen]. Therefore, the representation of space cannot be obtained through experience from the relations of outer appearance; this outer experience is itself possible at all only through that representation (Critique of Pure Reason A23/B38 as quoted at SEP).

The idea here is that space for the subject is not something we experienced and then abstracted as an idea. Instead, it 's something that we have to bring to our experience to experience anything in space:

  1. Space is a necessary a priori representation that underlies all outer intuitions (A24/B38-9 also from SEP).

For Kant, "space" is a concept we bring when we experience. This is a major part of Kant's philosophy -- the idea that we do not have unmediated access to an "out there." For some people, this sounds like crazy talk; for others, this seems obvious. But the basic picture for Kant is that we bring framing devices that structure our experience of things and what we encounter is structured according to them (to get technical we bring "manifolds of sensibility" in time and space and "categories of the understanding" (12 exactly for Kant) which we use to understand objects).

This highlights that Kant believes 2. To see that Kant does not believe 1, we go to the refutation of idealism which occurs only in the B version. Again, there's a helpful SEP article. The basic thrust of the refutation of idealism is that the time and space we experience really are linked to an out there and are not products of our imagination. (See this question for more discussion), but we experience them through the space and time we have as part of our knowing apparatus.

To give an analogy, Kant's view is that we have an operating system that loads in "time" and "space" before we can experience anything. And then if we want to understand an object, when we try to understand something we automatically bring concepts with us. For Kant, (on most sympathetic interpretations) this is not a denial of the underlying thing behind what we try to understand but only a statement of what we bring to the task of knowing.

Schopenhauer is not merely following Kant but removing the underlying realism about what is "out there." Maybe that makes Schopenhauer more consistent considering this is one of the stickiest problems in Kant scholarship.

  • Thank you. So you, as an expert, are saying that Kant believed we have an inborn and a priori concept/idea of time and space (a belief which today may be explained or supported scientifically based on the theory of biological evolution and natural selection), but he didn't assert or believe that things in themselves lack any sort of spatial dimension.
    – apadana
    Commented Feb 18, 2018 at 15:19
  • Interestingly, some contemporary scientists believe that space and time do not exist objectively. For example, in this TED talk, which I think will interest you, a neuroscientist argues in defense of this view.
    – apadana
    Commented Feb 18, 2018 at 16:10
  • 1
    @Arham You have to be careful: Existing objectively, for Kant, has quite a different meaning from what the TED talk might understand. Putnam quite explicitly argued that we cannot even understand what objectively should mean referring to outer objects. Kant in particular did not categorically rule out the possibility that things in fact are "really" exactly the way we perceive them, just that we could find any coherent truth condition justifying such a claim and hence should be agnostic towards claims about things in themselves and their properties.
    – Philip Klöcking
    Commented Feb 18, 2018 at 18:49
  • @PhilipKlöcking, I think philosophers have usually emphasized the difference between appearance and reality. And the existence of differences between these two is almost certain. For example when we study quantum mechanics or the theory of relativity, we see that the layman's conception of space and time and matter is so naive. But how large is the difference between how things are and how they appear to be? The opinions differ widely. If we believe Newton, the difference is not that much; If we believe Schopenhauer, the difference is incredibly large.
    – apadana
    Commented Feb 18, 2018 at 20:38
  • 2
    @Arham Kant is explicitly Newtonian, except he rejected the notion of absolute space Newton adhered to, writing that space is always relative to objects and other spaces.
    – Philip Klöcking
    Commented Feb 18, 2018 at 20:53

Quite an edifying thread, though I do have something to add. I would emphasize the question of how Kant's doctrines look, to somebody who finds this Kantian stuff perfectly cogent and persuasive. Kant on the subject of space and time, is certainly 'radical' stuff. There is something elusive going on here -- he's not saying what you expect somebody to be saying about it, it's nothing 'obviously reasonable'.

One of the replies is about how 'Can he be proved wrong? No. And it’s just like any other form of idealism,.. And can he be proven right? No he can’t by the same logic as above. Only god, if he exists, will ever really know.'

This 'accept the uncertainty' idea may seem prudent, but is not actually Kant's position. If we get into Kant's antinomies, then you can see that Kant takes himself to have proven that it gets paradoxical to suppose that space and time can be attributed to things in themselves. He has four antinomies in the Critique of Pure Reason, treating of whether maybe the world had a beginning, or did it exist forever? This is rather esoteric stuff, but to be catastrophically brief about it, Kant thinks both sides are wrong. This also damages the notion that space and time could maybe 'exist objectively'. If space and time are something like subjective requirements of our human sensory-cognitive faculties, then yes, we use these concepts empirically, so you could say that space and time are 'real', in the appearances. The appearances, are 'real', as being 'really appearances'. Note how Kant traces the apodictic certainty of mathematical judgments to the fact that we know all that we know about space and time with a priori certainty. That's not like things that exist objectively, which we hypothesize about, and speculate about. Space and time are added to every observation, by us, and are not self-subsisting realities, if that's the way to put it. All things must conform. Kant does not necessarily negate the idea of objective existence, but he's quite comfortable with some ideas like that God might transcend space and time. He even hints that God did not create space and time, we do. Kant shows that cognition of space and time is dependent on consciousness.

I suppose I can get as far as the idea of 'space and time' as frameworks through which we perceive and organize our sensory experiences, but then the question is why is everybody in the same experience of space and time? Seems pretty objective! Indeed, according to Einstein, space-time is warped by matter and energy or somesuch. It's theoretical physics. And I don't have any problem with Einstein. Maybe the relativity camp can lead us to expect that when it comes to space and time, it's okay if things start to sound bizarre.

You mention Schopenhauer, I'm not sure I'd emphasize so very much difference between Kant and Schopenhauer on this issue. I'll review a few points -- mathematics strikes Kant as evidence that we have a priori certainty of these mathematical judgments, because space and time are so dependent on our own forms of sensibility or such like, and also, if you ingenuously believe in an 'objectively real' space and time, you wind up with paradoxes anyways. When did the world begin? Can a coherent answer even be given? If the world began, then what event happened before it to cause it to happen? This may seem like another question for theoretical physics, is this about the big bang? A similar problem can be seen, though, with the size of 'the world'. I know that NASA will say how big is the universe, but that's the 'visible universe'. Beyond the visible universe, which, if it doesn't seem a bit odd, we find ourselves at the exact center of, there is more 'invisible' universe. So, does stuff just stretch out forever in every direction? That may seem like a logically coherent idea at first, but I'm not sure it is. If the universe is infinite, doesn't that have to mean that anything imaginable (as long as it's physically possible) exists somewhere? In other words, there's a planet that is exactly like ours, except Obama is a foot shorter, right? And one where guitars have seven strings? Infinite is not a clear thing. It doesn't really exist in most of our lives, but does it exist in science? You can't observe it. But you know all about how space and time work -- you know without being able to 'observe' it. Do you 'observe' time? Well, is it bigger than a bread box? This is abstract stuff.

Sticking to a Kant quote, time does not “attach to things absolutely, as a condition or property” (A36/B52 in Critique of Pure Reason).

Of course, talking about how time is subjective sounds like I'm saying that 'time flies when you're having fun'. But spacetime is a mathematical model. What is a mathematical model? The fabric of space-time is a conceptual model. Every time you sense something, every time you 'get an intuition', you assign space and time coordinates to it. Space, time, and spacetime are relational concepts like distance and temperature; they are not "things" in and of themselves..

Up the thread, I read that 'Kant in particular did not categorically rule out the possibility that things in fact are "really" exactly the way we perceive them'. Yes, he ruled it out, though there are two issues here. He ruled it out, but you might not agree with him. Kant puts emphasis on how we can know things with certainty, when we put those things in there to be known, and that is how we know space and time. I suppose that our empirical knowledge of space and time are 'really' exactly as we empirically know them to be!


Apologies if this contains any misunderstanding of Kant. He is the most difficult philosopher I’ve tried to understand due to his style and highly technical way of writing. And obviously the very abstract subject matter. Maybe Wittgenstein or Hegel also come to mind. I’ve included some of my own conclusions, so these could be wildly wrong.

One of Kant’s big ideas in the Critique of Pure Reason was named transcendental idealism. He saw space and time as a priori intuitions we have about the world. For example you are not taught about space and time but you intuitively grasp that it exists. Kant also did not see space and time as entities or substances, rather he saw them as forms of our intuition.

Kant thought (here comes the idealism) that if there were no humans around, there would be no space and time. Leaving us with just a world of things in themselves, another highly complicated concept which basically means, what objects are beyond our perceptions of them. This is absolute reality, beyond all sense perception. so if there’s no space and time, how do these things in themselves relate to one another. According to Kant they do this without recourse to space and time. As space and time are simply human intuitions, and not necessary for the mind of god. I may have butchered that last part, as the text is somewhat impenetrable.

So lastly, what does it mean for space and time to just disappear when there aren’t any human minds to comprehend it. This seems very counterintuitive as we think of other animals perceiving space and time no problem. And then even matter obeys space and time through Einsteinian laws and entropy, etc. Does Kant say that even matter wouldn’t exist without humans. It seems the answer is yes as without space and time there is nothing except for things in themselves. Can you perceive of a world without space and time? Everything around us would cease to exist, nothingness would ensue. Unless you could understand or apprehend the things in themselves, but we can’t, so that’s that. Maybe our souls could. Kant isn’t very clear on exactly what the noumenal realm is.

Can he be proved wrong? No. And it’s just like any other form of idealism, although it must be stressed that Kant still held there was an empirical (not clear as how you could have an empirical realm beyond the senses where empirical is by definition the realm of sense perception) objective reality (the noumenal realm) where the things in themselves reside. So all forms of idealism can’t be disproven, however counterintuitive they are. And can he be proven right? No he can’t by the same logic as above. Only god, if he exists, will ever really know.

I would say, if his ideas trouble you at your core, and you worry that you can’t know anything about reality for certain, I would encourage you to just accept the uncertainty and try to discover truths (no matter if they are not absolute) about the world, and marvel in their beauty if you can see it. Mathematics might hold the highest chance of certainty. But so do empirical questions. One could say, provided what we sense may not be the ultimate reality, I can still be sure about certain facts. And those facts are wonderful, maybe evolutionary history or general relativity. Whatever you choose to pursue. Find the truth in it even if ultimately you may be wrong. You could say if empirical reality (of our senses) is true then I know x,y,z. Even if space and time are just illusions, well you’ve had one hell of a ride enquiring into different things. With math which is independent of space and time, I guess in a way you escape kant’s grasp. Mathematics is still true no matter if space and time are physical aspects of empirical reality. Well at least the parts that don’t contain spatial relations. These things like geometry are incomprehensible in the noumenal realm as there is no such thing as space, so they may as well not exist.

we know from physics that space is geometrical. Wouldn’t that then make geometry also empirical? Kantians would respond that yes but there are other synthetic a priori mathematical facts which are independent of the physical geometry of the world. Another objection is that Kant neglects to acknowledge that the noumenal realm may have a geometry. He doesn’t mention this in his critique. But Kant would respond by saying that empirical knowledge of the noumenal realm is impossible as geometry is not contingent but wholly necessary and universal. Therefore there can be no empirical knowledge of the noumenal realm (beyond sense perception).

Now back to the point, which I believe is a stronger one, whereby space and time can actually eliminate parts of mathematics as just illusions based on our intuitions of space and time. Basically anything involving spatial relations, anything that can be mapped to a coordinate system, is simply illusory. Kant is saying that space and time aren’t objectively real beyond our experience of the world. Take away humans and space and time disappear, so wouldn’t that mean that large swathes of mathematics also disappear (all of geometry)?

Mathematics is a priori according to Kant. But in order for us to comprehend geometry we need an intuition for space. Without that intuition for space we can’t even imagine geometry. Therefore mathematics would be revised if you took away spatial intuition. The “real” world or the true world according to Kant doesn’t involve space or time so that would mean geometry also wouldn’t exist.

So that means math can’t be a priori as it depends on our intuitions (via taking away our empirical brains) and physical reality (space time is physically real as it interacts with physical matter). Take away our intuitions for space and time, and physical space and time itself, and geometry disappears, in the true world that is. In gods mind perhaps he can see all the possible kinds of mathematical worlds. But if we were ever to know somehow about (beyond just speculation) or exist in the noumenal realm (the spiritual realm, devoid of space, time, and matter) there could be no geometry, as there would be no concept, intuition, or phenomenon known as space. Unless we kept our human intuitions of space and time, but this is unclear.

One further thing about human minds being the key to space and time. It seems that other animals have an awareness of space and time. In fact even the most basic organisms like a bacteria, who don’t have a brain, have some sense or at least clearly respond to objects in their spatial environment. Inanimate matter obeys the laws of physics, so is in a relation to other spatiotemporal phenomena. To say that if there were to be no humans around to intuit space and time all of these things would cease to exist, seems highly self-centred and myopic. However if that’s reality, then that’s reality.

I haven’t read much German idealism yet, so I assume there are responses to Kant contained therein, and in the continental tradition more broadly. It would be interesting to see who picked up or critiqued Kant’s theories of space and time and the noumenal realm. As far as I know it’s had little impact on the analytic tradition outside of it being of historical interest and his ideas were used to a degree to attempt to relegate metaphysics into the dustbin of history, or used in the two dogmas paper, so I guess that Kant also had a big influence in analytic philosophy. But I guess that’s besides the point.

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