This is an older article by Sean Carroll (the physicist, not the paleontologist) that I recently read in Free Inquiry and wanted to link to here. He lays out the reasons why the idea that humans have an immortal “soul” (whatever that is; I’ve never seen anything even remotely like a coherent definition of it) is never actually turned into a scientific hypothesis:
Among advocates for life after death, nobody even tries to sit down and do the hard work of explaining how the basic physics of atoms and electrons would have to be altered in order for this to be true. If we tried, the fundamental absurdity of the task would quickly become evident.
Even if you don’t believe that human beings are “simply” collections of atoms evolving and interacting according to rules laid down in the Standard Model of particle physics, most people would grudgingly admit that atoms are part of who we are. If it’s really nothing but atoms and the known forces, there is clearly no way for the soul to survive death. Believing in life after death, to put it mildly, requires physics beyond the Standard Model. Most importantly, we need some way for that “new physics” to interact with the atoms that we do have.
Very roughly speaking, when most people think about an immaterial soul that persists after death, they have in mind some sort of blob of spirit energy that takes up residence near our brain, and drives around our body like a soccer mom driving an SUV. The questions are these: what form does that spirit energy take, and how does it interact with our ordinary atoms? Not only is new physics required, but dramatically new physics. Within QFT, there can’t be a new collection of “spirit particles” and “spirit forces” that interact with our regular atoms, because we would have detected them in existing experiments. Ockham’s razor is not on your side here, since you have to posit a completely new realm of reality obeying very different rules than the ones we know.
It’s like positing that the rain happens whenever an invisible leprechaun gets angry. Sure, we have good scientific models that explain why the rain happens and can predict it with a high degree of accuracy, but that doesn’t prove that the invisible leprechaun doesn’t exist, does it? Such a possibility can never be entirely disproved, especially when the actions of the supernatural agent can never be distinguished from purely natural events.