Of course it can be tempting to believe in the afterlife, because it reassures or comforts – perhaps we’ll see the loved one again, and perhaps (sometimes) we’ll get to shrug off some guilt we’re now left with because of hurtful things we said or did. But notice, especially with that last set of motivations, that selfishness is the governing principle, rather than a tribute to the deceased or the memory of them. If we did want to somehow acknowledge those that have left us, I’d imagine that satisfying the demands of our egos in that fashion would not be what they would recommend or hope for (if able to recommend or hope for anything).
But giving up on the belief in an afterlife does not mean that we have to give up on commemorating the lives of those we’ve lost. Rituals of significance are popular for all of us, even non-believers, and often deservedly so. They provide a narrative force that punctuates our existence, bookmarking our progress or regress, coming into and leaving existence. Weddings, birthdays, and funerals play this role, and we can engage in all of these sorts of things with as much or as little commitment to metaphysics as we like.
For a while, many decades ago, I used to light a candle on the anniversary of a particular person’s death, because he was such a treasured friend that I felt something was amiss if I didn’t remember him. Of course, that’s close to superstition. But it made me feel better, and that’s surely a respectable motivation, even if it isn’t the strongest one?
There is of course a range of significance to fictions, including the dabbling with the idea of an afterlife that might seem tempting in the immediate days after someone’s death. Fictions that allow you to sweep child molestation under the rug, to justify misogyny, or cause you to pray over a child while she dies instead of rushing her to hospital are clearly deeply significant. In addition to this spectrum of significance, it is to my mind indisputable that whether something is true or not matters.
In many cases, wishing that there were an afterlife is probably trivial. However, if a belief in an afterlife allows you to neglect duties in your “real” life, thinking you have time to make amends later, or allows you to think that your real obligations are in the hereafter rather than now (think, for example, of religiously motivated suicide bombers), then the belief can contribute to serious harms. And, because there aren’t any effective ways of preventing false beliefs from taking on these harmful forms, perhaps it’s better to avoid them as much as possible.
Even then, this shouldn’t mean telling the grieving mother that no, her child is not in heaven. But it does mean that we shouldn’t encourage such beliefs. And, not encouraging them doesn’t mean that we need to treat the deceased as if they never lived, or never meant anything to us at all.