No, it is more fruiful to say, "Prove there is..." because that's the basis of scientific/mathematical rigor. If you can prove it exists, it does. If you can't

No, it is more fruiful to say, "Prove there is..." because that's the basis of scientific/mathematical rigor. If you can prove it exists, it does. If you can't prove it exists, it doesn't, for all intents and purposes. You then act as though it doesn't, because until you can find evidence for it, it might as well be nonexistent, and you should act that way to be logical.