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So an objective solution would need to take into account what is good for mankind as a whole. IOW the survival of the human species. It needs to be an evolving relationship that adapts to a changing natural environment, relationships between separate and varied societies, and to the significant influence the study of history has on our awareness of what works and what doesn't.
This comment implies that
the human species is a coherent group with coherent and unified goals. Is that true? Will it ever be true? And if we're primarily concerned with the survival of our species, why not other species too? Why does our species take precedence? Is the survival of our species even a meaningful goal? If so, why?
I'm trying to approach the subject of morality as objectively as possible. If you want to look at it from a more personal, subjective point of view then I have to ask what standards you yourself use to arrive at an opinion of what policies your government should pursue. Does it have anything to do with what you believe other nations or peoples around the world deserve? Or how about people on the other side of your own country, or those who will be born after you and your family are long gone? We owe people our consideration simply because they are human beings. We do have unified goals, and they tend to encompass those things that benefit our well being and the well being of our descendants.
I'm sure we could think of a thousand examples of why our species is more important than any other. Mosquitoes, rats, cockroaches, various deadly bacteria to name a few. The species we consider important are the ones we find necessary for our survival, or things that seem to symbolize it. Butterflies and such. But I can try to answer your question of why we take precedence from an objective of subjective perspective. Subjectively we are born with an instincts that benefit our survival. Fight or flight and all that. And these are amplified by our cultural traditions. Objectively I need to step into the realm of metaphysics. All species have a basic instinct and genetic predisposition to survive. That's plainly not a coincidence. Things exist at all because they survive. Therefore it follows that the purpose of existence is survival. They are inseparable concepts. It is the fundamental requirement of all life at the level of species. There is no other answer to the meaning of existence. Despite the vain pleading of religions. And it's beautifully simple. Complexity springing out of simplicity.
To me
good for humanity is one of those phrases that sounds nice, but doesn't quite hit the 'objective' part you're looking for. It's easy, from a subjective point of view, to embrace humanity, but once we get into the realm of reality and law, humanity isn't a unified group.
Yes, if there is a major threat like Global Warming, or say, a meteor, it makes sense to band together on some level. But usually we're comprised of sub-groups, living in different regions, with different cultures, and different resources. It's not that we can't have respect for our species, and all life, on some level, but there is no such thing as
all human beings are equal under the law, and indeed there can't be. If that was truly our objective goal the nation state as sovereign body wouldn't exist anymore.
Furthermore I'm leery about the the survival of
our species being a meaningful goal, when evolution works on the individual, and the survival of individuals depend on the survival of nation-states, not humanity as a whole. Sure it might work as an ideal and sound nice, but in practice that's not how life on our planet works.
Lastly, basing our morality on what we are, a species meant to survive, seems short-sighted. If for some reason we're extending the goodness of our hearts to every human, I see no reason why this shouldn't extend to other animals as well. If we are good only toward humans, but not other animals, then it's not moral goodness on any level, it's just a manifestation of our survival instinct.