How about: Human life is the most advanced creation of evolution; the pinnacle of billions of years of evolution. No other life is as advanced. Therefore, human life is precious.
(I don't love the wording. But the idea is that, just as the greatest painting of a famous artist is precious, likewise the greatest production of evolution is precious. Not air tight, but maybe a start).
Good attempt, so I'll try to counter it, just to be argumentative.
As far as I know, the human body is no more complicated than most mammals. However, the human brain does appear to be unique in its capabilities.
So for human life to be precious, does it need to have a fully-functioning brain? Would that make the life of someone with severe learning difficulties, or even someone in a permanently vegetative state, less precious?
If you really do not believe that, by your own logic you should never defend yourself or kill anyone. Because if you're not precious to yourself, others might be worth more.
Otherwise you presume either hard equality between everyone (easy to rebuke) and/or omniscience.
Or you revert to consequentialist ethic where only consequences matter. (Not essentialist.) From that place, going from basic utilitarian ethics you can show what sort of value certain human lives had.
I don't think it logically follows that you should not kill anyone if you do not believe your own life to be precious.
For example, someone in a truly blind rage might go ahead and recklessly kill someone with complete and total disregard for his own life. While observing this act we might say that he does not believe his life to be precious because he acts as if it's not, yet he can nevertheless still be fighting and killing someone because he's driven by dark emotions.
I used the dictionary definition of "has high worth". The cutoff is indeed not defined.
However, the logic should be consistent for any bounded cutoff.
You could construct a system where everyone with lower than given value is subjected to some action.
Given your (or societal) bounded knowledge you then cannot generalise because you are not omniscient. This means you get to evaluate everyone on their terms.
This view is incompatible with stereotypes.
Alternatively you just assign values by axiom, which will likely end up with a big and likely inconsistent philosophy, unreliable guide.
Indeed egoism like this is a valid strategy but not an optimal one in absolute terms. (Tit for tat is stable instead over time.) A philosophy or strategy should be viable in the presence of a mixture of them.
> If you really do not believe that, by your own logic you should never defend yourself or kill anyone. Because if you're not precious to yourself, others might be worth more.
Survival instinct is powerful, it doesn't necessarily follow that exercising it means that you consider your own life precious.
You've chosen to raise complexity or "advancement" (snort) as the value pinnacle, but that's just your chosen value system. Any other metric could be just as true and consequently just as false.
If you have a red cube and a blue cube and a green cube, only one of the cubes is red. It is the reddest cube. Does being the most red make it precious? Is the blue cube precious because it is the most blue? The green cube? If you have a million cubes of all different hues, is each and every one precious because it is the most its-hue of all of the cubes? If each of the cubes is only mostly a cube, but actually deviates from being a cube in some way, is each one precious for being the most its-shape? But this one is the most pumpkin and the most missing-some-atoms-right-there! Ok, great. So what? So now everything is precious, because everything is the most of something? Let's congratulate ourselves and sing along with Monty Python, "Eeevery sperm is saaaacred....".
Or maybe being the most of something doesn't objectively carry any inherent value other than what we decide to put into it.
The thing I was trying most to emphasize was rarity. All else being equal, it seems that scarcity usually increases the value of something (I pose tentatively).
The greenest cube is very rare. It's the only one of its kind. Same with the reddest, and the purplest, and the pumpkinest, and the cubest, and the ...
> Human life is the most advanced creation of evolution
Arguable. It depends on how you define advanced. There are many organisms that live longer, are more numerous and can survive in more extreme environments than humans. It is also conceivable that humans might completely destroy all habitable environments, which would certainly disqualify us from the subjective qualification of "pinnacle of evolution". More importantly however, evolution has no pinnacle or direction.
Even if we grant that humans are "the most advanced creation of evolution", it does not necessarily follow that this causes it to be inherently precious.
From a strictly evolutionary point of view any other life, being our contemporary, is the pinnacle of the same billions of years of evolution and exactly as advanced as us. (Not that evolution is actually moving "forward", but it's fair to consider living organisms winners and extinct ones losers.)
To consider human life superior, we need less objective and more problematic criteria, e.g. claiming that we are special because we are sentient.
> Human life is the most advanced creation of evolution; the pinnacle of billions of years of evolution. No other life is as advanced.
This is a biased view of evolution. All species today are "the pinnacle of billions of years of evolution". Humans are not especially advanced, at least not in evolutionary terms.
There may be some argument to make about humans being especially intelligent, or something like that, but it has little to do with evolution.
And, to be fair, humans might end up wiping each other out via chemical or nuclear weapons, while ferns and tardigrades and bugs survive, so maybe we might not be so advanced after all...
