Ed Brayton at Dispatches from the Culture Wars dug up an article old article from Cosmic Variance about the physics of the soul. Conclusion: there is nothing in physics that supports the idea of a soul.
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.
But this will just provoke calls of “science doesn’t know everything” and “materialist!” and other such heckling. Regardless, I think even half of this argument is still damning to the case against life after death.
Perhaps there is a ghost in the machine that exists beyond all ability to detect it. Along with the ghost, we still have the machine. The machine does things, and we can prove them: stores memory, cogitates, experiences emotions and so forth. Almost everything we think of as a human’s mind comes from the machine. Take the machine away and you take the person away.
Perhaps there is some blob of spirit that will carry on, but without the machine what does it do other than simply exist? How is that blob of energy us if it doesn’t maintain our memories, personality thoughts and so forth? And it that blob of spirit isn’t us, how can we say that there is life after death?