The reason for believing in life after death is simply that there is no compelling reason not to, no objection to it that cannot be answered. The two most frequent objections are as follows:
(a) Since there is no conclusive evidence for life after death, it is as irresponsible to believe it as to believe in UFOs, or alchemy. Perhaps we cannot disprove it; a universal negative always is difficult if not impossible to disprove. But if we cannot prove it either, it is wishful thinking, not evidence, that makes us believe it.
(b) The strongest positive argument against life after death is the observation of spirit at the mercy of matter. We see no more mental life when the brain dies. Even when it is alive, a blow to the head impairs thought. Consciousness seems related to matter as the light of a candle to the candle: once the fuel is used up, the light goes out. The body and its nervous system seem like the fuel, the cause; and immaterial activity, consciousness, seems like the effect. Remove the cause and you remove the effect. Consciousness, in other words, seems to be an epiphenomenon, an effect but not a cause, like the heat generated by the electricity running along a wire to an appliance, or the exhaust fumes from an engine’s tailpipe.