It's an axiom, you get no justification.
I was asking
why it was an axiom. You attempt to defend why below:
It is arbitrary, and it is not at all about the right of the stronger. For example, implicit in that axiom is that a weaker human is considered more "valuable" than a strong animal.
You have to take an arbitrary position to start with. There are only three possibilities:
1) humans are more important than any other animals
2) humans are as important as some animals
3) humans are just as important as any other animal
Take your pick and explain why the first is less moral. I think you are confusing morals with a (misguided) attempt at coherence ("respect every living creature" hippie stuff). Personally I could make up "moral" arguments against any of those.
But I must point out that the third is also suicidal if one were to interpret it as "we must respect all other animals" as, inevitably, we're going to kill more than a few over the course of out natural lives. And the only other possible interpretation for 3) would be "we should use and kill other humans just as we use and kill animals".
I may as well go into detail and explain (again) why I disapprove of 2). And I have two reasons to disapprove. One is logic: because the choice of those some animals to protect will be made by humans, which will have to assume the role of judges - thus the very act of proclaiming some animals "equal to humans" affirms the superiority of the humans doing it... logical contradiction! And the other is moral: people are bound to disagree on which animals to protect, setting humans against humans allegedly for the sake of protecting animals, in reality for the sake of enforcing some human's preferences over those of others. Hardly a paragon of morality, to oppress fellow humans for the sake of some baby seals on the Arctic or "sea kittens" or whatever.
Really, there is no moral high ground on this, actually, it's a matter of preferences. And that's what irks me the most whenever those animal rights activists try to force laws to impose their worldview, and do it with all smug with presumed moral superiority.
And here I think you make a simple mistake. We do not have to conceive of the moral value of animals in one of the three ways you enunciate. Your framework supposes that each species has a certain intrinsic importance that makes members of that species inviolable. Your claim is that only humans have any intrinsic importance, so only humans are inviolable. We can do pretty much whatever we please to animals.
But we do not need to look at the issue in this way at all. We can claim that animals are
valuable without claiming that they are inviolable, and without claiming they arem ore valuable than humans. This is, I believe, the claim we would normally make about people. Human life is valuable but it is not inviolable; that is why we are allowed to kill someone in the ticking-bomb scenario.
I do not find this claim implausible nor necessarily arbitrary. If we have a plausible theory of value and animals have value according to that theory we can say animals are valuable. If we have a moral theory linking value to rightness (i.e. a consequentialist moral theory) we can say things about what we ought and ought not do vis a vis animals.
I can see little plausibility in any theory of value that would not give animals some of that value. We generally believe that happiness and pleasure are valuable; the world is in a better state if people are happy or experience pleasure than if they do not. Consequently, because animals can be happy and can experience pleasure their lives are valuable.
Again, that does not mean they are
more valuable than humans. I believe that the development of autonomy, the cultivation of appropriate personal relationships and the exercise of our rational capacities are of intrinsic value. Animals cannot, for instance, exercise rational capacity and therefore we need not conclude that each animal life is as valuable as each human life.
What it does mean is that we should take into account the value of animal lives when making decisions. Your claim denies that animal lives have any value and I believe that
that is arbitrary; you have not given a theory of value that would substantiate this. If we
do assign animal lives value than it is quite plausible that the pleasure you or I get from eating factory-farmed chicken is outweighed by the enormous suffering said animals underwent on their long way to the slaughterhouse. That does not mean we can do nothing with animals; keeping pets (for instance) does not seem to damage animals but is certainly of value to people. Indeed, we might still be able to justify some sort of meat-industry, in which the livestock are treated very well up until and including their being slaughtered.
What it means is that we take into account the interests of animals when we make decisions. We do not treat animals as if they were valueless and as if there suffering meant nothing, which is largely what we do today. We accept that human life is of higher value, but we assert animal life has value nonetheless. We assert this because animals are
capable of suffering and happiness, and these things are of disvalue and value respectively.
This conclusion is not touched by your contrary arguments. It is no contradiction* to assume the role of judges in such circumstances. We can judge because of our (valuable) rational capacities. But this does not entail that animal life is valueless simplicter.
Nor is this merely a matter of enforcing preference, any more than the assertion 'torturing people is wrong' is merely a matter of enforcing preference. I believe torturing people is wrong
because of the incredible damage it does to people and because of the disvalue of this damage. Similarly, the normative conclusion 'factory farming is wrong' is something one might believe because of the incredible suffering factory farming inflicts and the disvalue of this suffering. If the latter is 'mere preference' than so is the former; that it is a preference is suddenly not a criticism. If my view that 'torturing people is wrong' has normative significance despite it merely being an expression of preferences, so do views on animal rights.
As it happens, I do not believe either to be the expression of preference. I believe them to be assertion of moral fact; it is fact that torturing people is wrong and it is fact that factory farming is likewise. This is the case because some consequentialist theory is true and that theory has an account of value similar to the one I propose. We should not factory farm and we should not needlessly injure animals, even though human life is more valuable than animal life.
Your thinking goes wrong in that it is needlessly polarized. You seem to think we cannot have a sliding scale of value. When assigning value, and moral rights, we must assign it either totally or not at all. We must say either that a species (or animals in general) is absolutely every bit as valuable as humans or that it has absolutely no value whatsoever. But this is false. We can say that animals are less valuable than humans whilst still maintaining they have some value. This is precisely the position I have defended above, and I have elucidated some of the normative implication of this.
*The argument you propose certainly does not identify a logical contradiction, by the way. It would do so only if we conceived of 'equal' as 'equal-in-every-sense'. But we need not (and should not) conceive of equal in this way. In liberal democracies we claim that everyone is equal, but it is patently obvious that we are not equal in every sense. What we mean is morally equal; everyone has the same moral rights. Similarly, the claim that animals are equal to humans (a claim I do not endorse) should be construed as the claim that animals are morally equal to humans. They have the same moral rights.