If some mediums were real couldn't they produce a list of the fake ones? Dead people would know who the real ones were. Especially true of psychics etc.
Belief in any afterlife requires that you not know what being alive means.
Life is just our word for the process of living. It's not something put into people at birth that floats away when someone dies so it can't pop up somewhere else.
(And let's not forget that a fungus is alive too)
Humans are made up of the same elements as everything else. Just arranged differently. We're a mechanism that converts air, water and food into cells and energy until we stop.
We're just like a mechanical clock. It ticks until it stops, but is still the same clock. Just a stopped clock. A human can be resuscitated because nothing has left the body. It has just stopped like the clock.
If you believe humans have an afterlife you should also believe that clocks and toasters do. And why not? What did your toaster do to deserve being eternally dead?
Actually my new toaster tripped the circuit breakers so that little bugger is going straight to the fiery pits of hell.
[Gives phone a stern look] "and I'm keeping an eye on you too!"