Why do you care?
If you lived sinfully (as 75% of human population does according to Leviticus), what difference will it make if you start believing after your death? You get a lollipop and a heaven club-card?
Why do you think no-one returns from the dead to tell you "There is/isn't god up there and he blah-blah-blah"?
There is no after life.
There is no god.
There is no way to return.
There is no reason to return.
There is a damn-good reason you don't know if there is or isn't such deity and another damn-good reason that you are supposed to believe blindly or not at all.