"How do you know this for sure, considering you are still alive? How do YOU know there is no life after death?"
Hmmm, well to begin with, cellular functions require oxygen. Are you familiar with the CREBS cycle? Your consciousness is the result of neuronal ensembles firing within your cortex and brainstem, which also require oxygen and a blood supply. Now, last time I heard, the defnition of death precluded all of these functions, unless you have heard otherwise?
The second half of your question is what I call intellectual nihilism. Why? Because you are attempting to apply an inherently illogical premise (the positive assertion that the human body or "soul" somehow survives death) and redirecting the onus of proof on me, however, I am not the one making this claim, which is based upon NO EVIDENCE whatsoever. EXTRAORDINARY CLAIMS REQUIRE EXTRAORDINARY PROOF...................do you have any?
I, on the other hand, can produce hundreds of years of solid, empirical medical evidence demonstrating irrefutably that upon death, the brain ceases to function, and ALL cortical activity ceases to exist.
Naturally I can already hear the believer's rebuttal: Ah, but you dont KNOW that our "consciousness" is defined beyond the limitations of biology!.....However, I DO know this is the case. Do you need proof? Consider the hundreds of thousands of examples of people having their entire personalities, consciousness, perceptions changed simply as the result of a biological process happening within their brains....schizophrenia, alzheimers, LSD, the list goes on ad infinitum.....In short EVERYTHING you think, everything you are, everything you were or will become, is determined within an electrochemical synapse between neurons within your brain. Thats it. The cortex dies, the "soul" or whatever else you wish to call your "sense" of self or sentience, will die right along with it. I suggest you get used to this simple fact of life......