Descarte gave multiple logical arguments for a god that is capable of creating an afterlife.
- (1) Our idea of God is of a perfect being, (2) it is more perfect to exist than not to exist, (3) therefore, God must exist.
- (1) There must be as much reality in a cause as in an effect, and so, (2) there must be as much formal reality in a cause of an idea as there is objective reality in an idea. Since we have an idea with infinite objective reality (namely, the idea of God), Descartes is able to conclude that there is a being with infinite formal reality who caused this idea. In other words, God exists.

Thomas Aquinas too:
-The unmoved mover argument asserts that, from our experience of motion in the universe (motion being the transition from potentiality to actuality) we can see that there must have been an initial mover. Aquinas argued that whatever is in motion must be put in motion by another thing, so there must be an unmoved mover.[18]
Aquinas' argument from first cause started with the premise that it is impossible for a being to cause itself (because it would have to exist before it caused itself) and that it is impossible for there to be an infinite chain of causes, which would result in infinite regress. Therefore, there must be a first cause, itself uncaused.

-The argument from necessary being asserts that all beings are contingent, meaning that it is possible for them not to exist. Aquinas argued that if everything can possibly not exist, there must have been a time when nothing existed; as things exist now, there must exist a being with necessary existence, regarded as God.

-Aquinas argued from degree, considering the occurrence of degrees of goodness. He believed that things which are called good, must be called good in relation to a standard of good—a maximum. There must be a maximum goodness that which causes all goodness.

-The teleological argument asserts the view that things without intelligence are ordered towards a purpose. Aquinas argued that unintelligent objects cannot be ordered unless they are done so by an intelligent being, which means that there must be an intelligent being to move objects to their ends: God.

Pascal's watch is another argument.

This is just from a quick wiki search.

George, so it's not that people who believe in God and an afterlife are delusional or illogical. There is logic involved. However, logic can be based on false premises. For instant Newton's universal law of gravitation is logical but we now know it is based on false premises. I used Newton for this example because he believed in a god. He believed physics was the way to understand god's mind. Are you to say this empirical man of science who developed optics, worked out gravitation and calculus is delusional and illogical?
A note on explanation. Science answers the how questions, religion and the humanities answers the why questions. If we took a war, and looked at it scientifically all we would see is matter in motion. No where would we see a REASON(justice, equality, devotion) that would have started the war. The same might go for humanities existence. Maybe it was created by an intelligent designer for a reason. If your a scientific man, then by Hume's deductive principle you can't be sure about anything for certain. You may claim it is improbable but that's as far as you can go. Just consider them optimistic.

Let's not throw words around lightly but comment gently. This is a dance not a war.