This question stems from my scant knowledge on dark matter which supposedly seem to constitute almost 95% of our universe together with dark energy, this matter is one which we cannot interact with and can't even measure but know that it exists because of the expansion of our universe that was observed as a result of redshift in the Cosmic Microwave Background radiation, I think.

The other being that without this matter's gravitational effect, we wouldn't have the structure we observe in our universe because it seems to act like the beam for the universe holding it together via its gravitational effect.

Now we can't really say that we know this thing but only the effect that seems to happen. We can't interact with it or our machines and study it but we can only see it's effects, so is it rational that such a thing exists or is this just some weird assumption/theory/explanation some physicist came up with just because the math didn't align with the state of the universe and so someone had to come up with some random variable that explains it.

Edit: what I mean by this is that without "dark matter's" effect our understanding/observation wouldn't make sense i.e., the math would be inconsistent with the observation and so is this why physicists were like well there must be something causing this great gravity that we can't see or interact with. Something analogous Newton did with the Aether.

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    Strictly speaking, "know a thing without any properties" is incoherent, that we can know it is its property and so is being a "thing". But taking "any" loosely, Kant says yes:"Though we cannot know these objects as things in themselves, we must yet be in a position at least to think them as things in themselves; otherwise we should be landed in the absurd conclusion that there can be appearance without anything that appears." 'Pure existence' proofs in mathematics are similar, they prove existence of objects answering a specification without giving any information beyond the specification.
    – Conifold
    Commented May 6 at 3:55
  • @Conifold That still seems to be a contradiction. If I see a ball in front of me, and I can’t know this object in itself, then how does me not thinking that it is an object in itself imply that there is an ‘appearance without anything that appears’? As an analogy, the appearance of a tree in a video game does not require us to think that there is a thing in itself that corresponds to a tree. One can perhaps think of a thing that generates the appearance of a tree but not a thing that corresponds to the tree itself.
    – Marriott
    Commented May 6 at 4:19
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    Kant says nothing about "correspondence". As there is an appearance, of a ball or a tree, there is something that appears, be it an actual tree or computer pixels. Whether the something "corresponds" to the appearance in any sense makes no difference, we are only after pure existence. That is why Kant can say that things in themselves are unknowable beyond what follows from their specification as such. Even the plural "things" is misleading, there may well be just one single Thing behind all appearances, for all we know.
    – Conifold
    Commented May 6 at 4:31
  • Your title: Can one know something (a thing) exists... indicates a general question. But your question itself only refers to 'dark matter': is this just some weird assumption/theory/explanation some physicist came up with just because the math didn't align with the state of the universe... Please clarify.
    – Vector
    Commented May 6 at 5:17
  • @Vector I hope my edit clarifies what I meant by the assumption physicists came up with!
    – How why e
    Commented May 6 at 20:34

1 Answer 1


The situation you describe is exactly how it was when physicists began to suspect the existence of the neutrino, which was the means by which the math could be fudged to match the experimental results.

It then took decades of work to invent the technology needed to detect a single neutrino- a feat that won its inventors the Nobel Prize, many years after its existence and properties were first hypothesized.

  • I know this and I watched a documentary about this, but doesn't this mean there is always something out there that there is no mathematical descriptions for yet but actually does exist? For example, say multiple infinite dimensions.
    – How why e
    Commented May 6 at 4:16

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