A Fear Of Death

Death might not be feared by all people, but anything other than a vague, irreducible fear of death (irreducible in that there are no more foundational desires or fears here) is always really one of two things.  It is a fear of nonexistence or a fear of a hypothetical afterlife, which is in turn terror at an afterlife existing at all or at whether an afterlife would be full of agony.  There is literally no other reason why someone would fear death unless they simply dread it just because they happen to subjectively dread it.  There is not an infinite chain of desires or fears lurking beneath a given fear, or else it would be impossible to actually experience any of them at all, but there is only a very limited number of more specific motivations behind a genuine fear of dying.

A terror of nonexistence can itself have several different manifestations, such as a personal reluctance to not exist because one wants to continue having conscious experiences or sadness over an inability to help surviving friends or family members.  Even so, all of these are ultimately just variations of fearing nonexistence itself or what would follow from one's nonexistence as a conscious being.  Fear is indeed subjective.  Not everyone fears the idea of their consciousness coming to an end regardless of the metaphysical ramifications (for instance, permanent nonexistence of consciousness means there is no possibility of experiencing pleasure or fulfillment in any form) or because of what life will be like for those still living.

There is still much to the nature of having and then forever losing consciousness that people might fear, for to live a fairly short life when death could spring upon you at any moment and forever claim you is something with massive metaphysical and personal implications.  For some people, though, the fear of death could be about the opposite: rather than nonexistence, existing forever or even for a limited time after the death of the body is a terrifying concept.  The reasons could range from a morally apathetic person hoping there is no such thing as a deity with a moral nature waiting for them to die (though even an amoral deity could contrive an unwanted afterlife) to someone who has experienced great suffering hoping for an eternal lack of pain.

Non-rationalists, in some ways, have more to fear about a hypothetical afterlife or lack of it precisely because they are so irrational, either failing to reason out logical truths about the notion of an afterlife (such as that it is logically possible for there to be an afterlife, that it might be undesirable, or that there might not be one at all) or feeling afraid because they have assumed something about whether there is or is not an afterlife, or perhaps about what it is/would be like.  Rationalists, still, might have their own deeper motivations for fearing an afterlife or lack of one.  It is possible that there is an afterlife of misery for all people even if there are no moral obligations and thus no justice for a deity to uphold; it is possible that even though there is an uncaused cause, there is no afterlife despite there being nothing logically impossible about one existing.

Regardless of whether human consciousness persists after bodily death or which of the many logically possible forms an afterlife could take (anything that does not contradict itself and necessary truths is possible, after all), not everyone fears death, what comes or could come next, or eternal life or death.  Some people might experience fear or its absence for idiotic reasons, as they have made assumptions or chosen a philosophical apathy that influence their emotions regarding the issue.  Others might fear death or its absence because they desperately want reality to feature moral obligations and for deeds to direct people to an afterlife of peace or punishment accordingly.  The logical possibilities for an afterlife, the necessary or contingent relationships between an afterlife and separate, verifiable metaphysics, and one's personal feelings and preferences about the matter are knowable even if the existence of an afterlife is not, and these truths could easily spark or calm fear depending on one's subjective emotions.