Simple scientific procedure :
1) There's no scientific theory that would explain that our "spirit" still live after our death. At the opposite, we can easily conceive that our "spirit" (or soul or personnality or whatever you called it) use our brain as an hardware support and that destroying the hardware also destroy the spirtir/soul/...
2) There're are no fact that could lead us to think after-life exists (from a scientifical point of view)
3) There are no facts that could be explained in an easier way if we admit the existence of an after-life. Instead, it makes things a lot more complicated.
Any logical mind would infer that after-life do not exist (or has little chance to do) from one of those 3 points. So the 3 points together make it highly logical that we just die with our body.
I know that some will invoke traditions and culture, telling that, if people believe it or even have evidence, it might be true. Yeah, sure. Same apply for Little tooth fairy, santa claus, UFOs and God.