God's Existence And An Afterlife: One Does Not Follow From The Other

If people only believed in God, across all the varying forms of that belief and its ramifications, out of a desire to have eternal life in an afterlife, then no one would ever even consider, believe in, or probabilistically gravitate towards something like non-religious theism or deism.  In a purely rationalistic sense, it is obvious that the existence of an uncaused cause (God) and the existence of an afterlife for humans have no inherent connection no matter what assumptions many people make to the contrary.  However, because so many prominent religions feature somewhat specific details about an afterlife, especially Christianity, the typical thinker, who is already not a rationalist, fails to avoid believing that theism is inherently religious or that it automatically entails an afterlife of some kind.

This is ultimately a classic example of an unwillingness to separate ideas that are not linked by logical necessity except in very particular religious contexts.  If Christianity is true, there is an afterlife directly related to God's nature.  If Islam is true, there is an afterlife directly related to God's nature.  If a deity with no moral nature who is uninterested in human affairs is all that the uncaused cause amounts to, then there might not be an afterlife at all.  The existence of an afterlife does not logically follow from the existence of God.  Actually, the inverse is true as well: it would not logically follow from the existence of an afterlife that God exists, though an uncaused cause exists by logical necessity.  This is not particularly difficult to prove.

In fact, even some actual or hypothetical religions might not involve the idea of an afterlife.  Basic theism certainly does not (though theism is not a religion at all by itself).  After all, mere theism only posits that a deity exists, and even then basic theism being true does not require that this deity has a personal relationship with humans, any sort of moral nature, or any sort of post-mortem experience for humans.  All religions, as opposed to the arbitrarily broad range of things some people might erroneously call religions (like secularism or any ideology at all), involve the existence of a deity or pseudo-deity (not an uncaused cause, but something regularly mistaken for an actual god regardless, like Zeus), but not all theism is religious in nature on a conceptual level.

An atheist could believe in an afterlife and not contradict their atheism, despite the irrationality of believing that there is an afterlife as opposed to believing it is possible or even probable (given the evidence for the Bible.  A theist could believe that there is no afterlife--the latter belief is irrational but not inconsistent with being a theist despite the provability of the uncaused cause's existence and the unprovability of an afterlife.  The rationalistic stance, given human epistemological limitations, is to not believe that an afterlife must or must not exist, for either of these is possible and neither is true by pure logical necessity in and of itself.  Whatever the truth about the issue of an afterlife's existence is, it does not contradict any necessary truths or what follows from them.