As would your knowing that there is life after death. To know that aside from believing it would have to mean you died went to heaven and were there long enough to recognize it as such, and then returned here to earth to tell us about it. No human being has ever done that. I suspect you are also a human being; I can't verify you are.<quoted text>
If you are sure there's no life after death that would mean you have died at some point and time and came back to life to tell us.
How long were you dead? A couple of days? What brought you back to life Frankenstein? Electricity?
Personally, I do not "know" there is no life after death, but I do know that the sources from which man draws that idea are not reliable, because they have been proved to not be reliable, and the most logical explanation for that, for me, is that they are fictional, and thus no man knows there is anything after death.
What we now know about what constitutes conscious life tends to indicate that all of that ends when the body no longer is alive, because we can demonstrate with the physical body the various physical signs which indicates that consciousness has a physical component which is entirely dependent on the ability of that part of the body to function.