The question seems to be about a need to know if we continue in some identifiable way, a continuing something that resembles what and who we are now. The thought of "nothing" seems too unbearable for many people. I think the question is also about what has happened to those we have loved and who have died, what about them? Are they OK? Will I see them again?
The short answers, "Yes of course there is life after death!" and "No, this life is all you get!" are for me both too simplistic. My honest answer to my student is "I don't know."
The student rejoinder, "So you don't believe in life after death?" Is followed by my response, "That is not what I am saying. I am simply saying I don't know."
For how could I? I have never died. The millions and millions of people who have died are the only ones to know, if knowing is part of the "afterlife," and the dead do not communicate with us. I am prepared to be bombarded with friends who will tell me that they "feel" their loved ones, that they talk to them, and that they feel comforted by their presence. Surely, such feelings prove that their loved ones are still "alive" in some way. I will not argue with the experience. But such experiences are open to various interpretations. When people feel comforted in such ways, I am happy for them—genuinely happy for them. But, it does not translate for me into knowing that there is life after death.
What justifiable reasons would amount to being able to say "I know"?
Personal experience is one such reason, and I do not dismiss experiences lightly. Not long after my father passed (in 1989), I was in our kitchen and spoke aloud to my dad, who I thought was just behind me. I turned and there was, of course, no one there. It was in the first few days of grief. Though I often think of him, I have never had a similar experience. Did the experience lead me to know that loved ones continue after death? The incident has multiple interpretations. I cannot say on the basis of it that I know.
Other reasons offered for knowledge are religious myths, stories of the ancients who did amazing things, raised the dead, ascended to heaven in a chariot, walked out of their graves. These are inspiring symbols that life overcomes death to be sure. But literal happenings? I think it is doubtful, based on all our other experiences of life. And even if literally true, what meaning might it have for us? Better the symbol of the strength of life.
Religious authority might be another reason to know things. Here, I confess to skepticism, as religious authority is claimed for all manner of egregious practices. Because a religious leader, or a religious book, tells me something does not make it true.
Perhaps the evidence of sheer numbers might make something true? If so many people believe in "life after death," then surely it must be true? In times past, most people believed the earth to be flat. Weight of public opinion does not make for truth.
Finally, intuition might lead us to truth. "I know because I simply know." "I know it deep down." The problem with such subjective claims to truth is that subjective claims conflict with each other. How do I choose between them?
So, when my student asked me, "Professor is there life after death?" I still must say, "If you mean that you personally, your individual consciousness, all that is you in your uniquely mental life, will continue when your body dies, I do not know."
But my tradition is Christian. And at this time of the year, the season of Easter, we gladly say "Christ is risen! Risen indeed!" For me, our Easter season is an evocative celebration of life. In the Northern Hemisphere it coincides with the newness of spring, with all around in bud, expectant, ready to burst into the glories of summer. (My friends in the South will have different symbolic representations of the season.) It is a season of hopefulness, of joy, of being thankful for life.
Nature is cyclical. Death follows life. And just as surely life follows death. Nothing "goes away." Everything recycles into something else. In nature, death is a transition to life. So, that which dies becomes one with that which lives. I suppose, in the end, each individuation returns to the One. I am content to rest in that, without a claim to knowledge.
Enjoy the springtime transition,