All animals have an inherent instinct to drive them to live until the inevitable.
To live is equivalent to they should not die. [cup half full = half empty]
To ensure they should not die, they have to run away from the threat of death.
It is more direct to interpret as animals run away from the threat of death rather than say, run away to live.
The mechanism that triggers the animal to run away from the threat of death, is the mechanism of fear that is within brain.
While the animal will not deliberate on it intellectually, from the human perspective [scientifically and otherwise] there is “fear of death” neural circuit in the brain of animals.
Yes, animals do not have concept of death nor any consideration for any concept because their brain has not evolved to deal with things conceptually as human do.
But if we think deeper, within the animal brain, there is a semblance of ‘concept’ like concepts in humans.
Why should I think that the instinctual behavior in humans is much different? Humans can consciously think and understand death. But why would their instincts be driven by fear of death when animals don’t seem to be driven by such a fear? I don’t see any good reason for the instinct to change in that way.
That’s why I don’t think that P1, P2 or P3 are true.
It is very obvious the human brain is extraordinary different from all other animals in terms of mental performances and the degree of self-awareness and self-consciousness.
The “fear of death” neural circuit in the brain of higher animals [primates and other mammals] are similar to that of human beings. Note,
https://en.wikipedia.org/wiki/Fear#Neurocircuit_in_mammals
en.wikipedia.org/wiki/Fear_proc … _the_brain
Researchers have found that fear is established unconsciously and that the amygdala is involved with fear conditioning.
Therefore that is “fear of death” neural circuit within the subconscious brain of all human beings.
This is the subconscious fear of death in the brain.
Because it is subconscious fear of death, the human being is not conscious of it.
However the turbulent subconscious fear of death as fed by evidence of death morph its impulses indirectly as existential anxieties, despair, hopelessness, Angst.
Because it is indirect, the human being is not aware it is from the subconscious fear of death, but the person experiences all the indirect existential pains as anxieties, despair, hopelessness, Angst.
Because these existential pains are felt consciously, the human being has to deal with it.
The majority soothe such existential pains via theism which actually give immediately results.
Since theism has its cons, Buddhism [& others] came up as an alternative to deal with the cons from theism.
So what is the proximate root cause to all the above is the subconscious fear of death.
Fear processing in the brain
By understanding how fear is developed [unconsciously] within individuals, it may be possible to treat human mental disorders such as anxiety, phobia, and post-traumatic stress disorder.
en.wikipedia.org/wiki/Fear_proc … _the_brain
That is what Buddhism-proper is attempting to do, i.e. by understanding the subconscious fear of death and treating the existential anxiety spiritually, not as a mental disorder.