If scientists proved that there is life after death, would most people rather die than remain alive?
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The answer to this question is subjective because many people are enjoying their present life. Then why should they commit suicide and end their life? So the answer to the question depends on their present condition (their living condition, age, ailments, relation etc.)
Many philosophers have mentioned that this life is a continuation of a past life. If you try to analyze people's abilities, you can't disprove this. See, they are not well-known scientists. The only thing you need is a keen power of observation and a keen power of analyzing. If so, if you believe the words of philosophers what would you do? From your question I believe you have stronger faith in scientists than in philosophers. If scientists can't assure whether the next is human-life and it is here, most people never think about ending their life. So the people's decision depends on faith also.
Some innocent people might think: "How could I live again in this peaceless world suffering many difficulties? So I should try my best to make this earth a good place for my next birth. So I must live here as it is now as far as possible."