There is no ought or the way things should be once you accept metaphysical naturalism. If everybody started killing each-other, that event would be no more or less significant than if everybody decided to help each-other to survive.
I accept this. If metaphysical naturalism is accepted, there also is no prohibition against – as I noted in another thread – eating fetid garbage, swallowing needles, and ingesting poison (what will
never be objectively true, however, is that such behaviors are healthy to the human organism).
There is little chance of many “sane” human beings – including the most anti-social criminals – adopting this behavior. If we did have ancestors who consciously chose things such as this, none of them are left to tell us about it.
Likewise, there is no prohibition against the purpose of the medical professional being to maximize harm of the patient (the anti-Hippocratic oath); from fire departments being established to start fires; and for rape, murder, and violent theft to become mandatory, on pain of imprisonment .
But there is little chance of that gaining common currency in human society, either (if it had, we would not be here to discuss religion and the meaning of life, or anything else).
It is not possible to exterminate the will to live in the majority of even intelligent human beings, any more than it is possible to exterminate language or thought from human existence. It’s just the way we are hard-wired, and–by all appearances – our very rationality exists because it was a very effective means of keeping us alive. Rationality was the means; survival was the end, even though – as many human beings have done with sexuality – rationality now becomes perceived as an end in itself, and it whiffs at something so mundane as self-preservation (or the propagation of the species).
Our very God concept may have evolved precisely because we desire life so much, nothing but immortality will satisfy us.
It’s just as simple as that – as long as we prefer life over death, and pleasure over pain, what we call personal wisdom will be foundational (e.g., it is not “wise” to drink paint, or to put your hand down a garbage compactor), as well as what could be called social wisdom (hospitals should *treat *patients; fire departments should *extinguish *fires; laws should protect). Rightly or wrongly, we don’t have much use for an individual who is a sociopath or a violent criminal, any more than we have tolerance for poison in the vicinity of food.
I might as well ask why I don’t have three limbs, or four eyes. It’s as fundamental as my very anatomy, however demeaning it may seem to certain individuals that they were born as mammalian creatures with certain natural “preferences”, one of which is the desire for life; another which is the desire for happiness. If these natural preferences didn’t exist, ironically, morality itself would not be necessary, because no one would have minded if anyone killed them, or caused them pain. Society itself, likely, wouldn’t exist – nor would we. Nor, sadly, would any concept of God – in a human brain, at least.
But as for selfishness – yes, we are selfish. Case in point – we value human life more than animal life. Humans come first. We did
not need God for us to come to that conclusion; that is humanity’s love and preference for itself.