Why? According to chaos theory every single action we take in any life has uncalculable further consequences for the light cone traveling outward into the universe from the moment the action was taken.
Chaotic systems in nature aren’t actually non-deterministic. Their behaviour is still entirely determined by their initial conditions, which are physical. Their evolution is just highly sensitive to differences in initial conditions. That the weather is chaotic doesn’t mean that the weather has non-physical causes or effects.
It seems pretty clear that the proximate cause of my behaviour is neurons firing. For example, neurons fire and cause my muscles to contract. Neurons are merely composed of matter, therefore their behaviour is described by the laws of physics (eg, the Standard Model of particle physics). Neurons fire when physics says that they will fire.
If karmic traces are going to have some influence on my physically observable behaviour, then it seems like there’s going to have to be some cause of my neurons firing which isn’t some cause found within physics. They will have to fire when physics says that they will not fire.
If I have a memory of juggling, and say “I can remember juggling”, my neurons fire so as to cause me to vocalise in this manner. The cause of these neurons firing is just other neurons firing, and, further back, a chain of various biological phenomena going back to my conception.
As far as I can see, there is no reason to suppose that this causal chain is not the one which would be predicted by our current theories of physics. If there are to be past life memories, then it seems like we’d have to have some sort of causal chain going back from my saying “I remember doing X in a past life” which includes some element which would not be predicted by our current theories of physics.
Perhaps the firing of the neurons which cause me to vocalise a past life memory cannot be accounted for by physics (maybe memories aren’t in the brain at all). Or perhaps the neural structures which constitute my memories arise from causes which are not contained in our current physical theories (eg, some sort of immaterial spirit which moves from body to body).
I’m inclined not to believe in rebirth because I don’t really see any evidence which suggests that either of these things are the case.
I don’t really think that any of this is outside the bounds of empirically observable phenomena, so I don’t really think that one can insulate the theory of rebirth from empirical refutation. The theory seems, at least implicitly, to make claims about the behaviour of publicly observable phenomena. It seems to suggest either that memories aren’t in the brain at all, or that, if they are, then the structure of a person’s brain isn’t solely determined by what has happened to them in this life.
Then you have QM and entanglement and the influence of subatomic particles entangled with other subatomic particles no matter the distance.
I’m not sure of the significance of this to rebirth. It’s astronomically unlikely that a significant amount of the particles composing my parent’s gametes would be entangled with those composing some other being which was about to die so as to affect my early development. It’s not even clear how, even if they were entangled, such entanglement could have the effects which seem to be required for the theory of rebirth.
And that’s even assuming we actually know the physical laws; which we manifestly don’t. QG hasn’t even been figured out yet.
It seems like we have a pretty good grasp of the behaviour of objects that are about the size of human brains. Human brains are well within the domain of applicability of QFT.
Is there any reason to think that this is the case? Even if you are going to posit non-physical causes for the collapse of the wave function, why posit kamma? Maybe it’s ghosts, immaterial souls or god.