Hmm, well, science doesn't say any of that. Scientism might, but scientism is just a religion in disguise.

There's a wonderful story about Carl Sagan's encounter with the Dalai Lama. Sagan, an avowed atheist, once met the Dalai Lama and, in the course of their conversations, asked, "What would you tell Buddhists if science could prove there was no such thing as reincarnation?"

He probably expected an argument. Instead, the Dalai Lama replied, "Then we would tell them to stop believing in it."

After a beat in which Sagan had no answer, the Dalai Lama added, "How would you go about proving that?"

And again, Sagan had no answer.

Here's the problem. Science deals with the workings and history of physical reality. If there is something beyond physical reality, the methods of science have no way to access it. Now, it could be there would be some clear difference between a physical world that was cojoined with a non-physical world and one that is not, but since science can't access a hypothetical nonphysical world, it has no clear way to determine what those differences might be.

I have had one or two experiences that convince me such a world exists, but you could argue that those were just something funny happening inside of my brain. You can't prove that was the case, and I can't prove it wasn't the case. So any argument over it would be pointless. It's rather like a brilliant line from the final installmnt of Harry Potter (at least the film version; I'm not sure if it's direct from the book): "Of course it's happening in your head, Harry. Why should that mean it isn't real?"