"The antispeciesist claims that, other things being equal, conscious beings of equivalent sentience deserve equal care and respect."

Any speciesist is happy to agree with that. She simply thinks that species is one of the things that has to be equal.

Vanvier, do human infants and toddlers deserve moral consideration primarily on account of their potential to become rational adult humans? Or are they valuable in themselves?

My intuitions say the former. I would not be averse to a quick end for young human children who are not going to live to see their third birthday.

But their lack of cognitive sophistication doesn't make them any less sentient.

Agreed, mostly. (I think it might be meaningful to refer to syntax or math as 'senses' in the context of subjective experience and I suspect that abstract reasoning and subjective sensation of all emotions, including pain, are negatively correlated. The first weakly points towards valuing their experience less, but the second strongly points towards valuing their experience more.)

None of the above criteria except (in some empirical cases) H imply that human infants or late stage demented people should be given more ethical consideration than cows, pigs or chickens.

This strikes me as a very impatient assessment. The human infant will turn into a human, and the piglet will turn into a pig, and so down the road A through E will suggest treating them differently.

Similarly, the demented can be given the reverse treatment (though it works differently); they once deserved moral standing, and thus are extended moral standing because the extender can expect that when their time comes, they will be treated by society in about the same way as society treated its elders when they were young. (This mostly falls under B, except the reciprocation is not direct.)

(Looking at the comments, Manfred makes a similar argument more vividly over here.)

I think suffering is qualitatively different when it's accompanied by some combination I don't fully understand of intelligence, self awareness, preferences, etc. So yes, humans are not the only animals that can suffer, but they're the only animals whose suffering is morally relevant.

The general consensus is that at this stage, it's most important to raise awareness about wild animal suffering so future generations are likely to do something about the issue. This is done by spreading anti-speciesism and by countering the view that whatever is natural is somehow good or that nature "has a plan". It seems especially important to try to change the paradigm in ecology and conservation biology in order to focus more attention on the largest source of suffering on the planet. Some altruists also focus on this issue because of concerns about space colonisation, for instance, future humans might want to colonise the universe with Darwinian life or do ancestor simulations, which would be very bad from an anti-speciesist point of view.

Some imagined long-term solutions for the problem of wild animal suffering range from a welfare state for elephants to reprogramming predators to reducing biomass, but right now people are mainly trying to raise awareness for more intuitive interventions such as vaccinating wild animals against diseases (which is already done in some cases for the benefit of humans), not reintroducing predators to regions for human aesthetic reasons, and helping individual animals in distress as opposed to obeying the common anti-interventionist policies in wildlife parks.

Actually, I'm an eliminativist about phenomenal states. I wouldn't be completely surprised to learn that the illusion of phenomenal states is restricted to humans, but I don't think that this illusion is necessary for one to be a moral patient. Suppose we encountered an alien species whose computational substrate and architecture was so exotic that we couldn't rightly call anything it experienced 'pain'. Nonetheless it might experience something suitably pain-like, in its coarse-grained functional roles, that we would be monsters to start torturing members of this species willy-nilly.

My views about non-human animals are similar. I suspect their psychological states are so exotic that we would never recognize them as pain, joy, sorrow, surprise, etc. (I'd guess this is more true for the positive states than the negative ones?) if we merely glimpsed their inner lives directly. But the similarity is nonetheless sufficient for our taking their alien mental lives seriously, at least in some cases.

So, I suspect that phenomenal pain as we know it is strongly tied to the evolution of abstract thought, complex self-models, and complex models of other minds. But I'm open to non-humans having experiences that aren't technically pain but that are pain-like enough to count for moral purposes.

This seems to address one of my points raised here.

Self-mutilation is certainly a proxy for very low or negative quality of life, even if directly suicidal behaviour is not available (because the animal can't form a concept of suicide as a way out). If the docking, castrating etc. is to prevent mutilation of other nearby animals, that's a bit different of course.

I'm very wary of deeming any life to be of negative quality unless there is very compelling evidence that the life-form itself feels the same way.

Also, see my other comment: what happens if a few changes to farming practice can make the quality of life positive, even if just barely so? Does the objection to meat really go away?

Have you read much about the lives of farm animals? In general once people do I think they agree that these are lives that are not worth living. There's plenty of footage on the web too.

Humanity's only justification of exploiting and killing nonhuman animals is that we enjoy the taste of their flesh.

It seems to me like a far more relevant justification for exploiting and killing nonhuman animals is "and why shouldn't we do this...?", which is the same justification we use for exploiting and killing ore-bearing rocks. Which is to say, there's no moral problem with doing this, so it needs no "justification".

Pigs, for example, are at least as intelligent as prelinguistic toddlers; but are they less sentient? The same genes, neural processes, anatomical pathways and behavioural responses to noxious stimuli are found in pigs and toddlers alike. So I think the burden of proof here lies on meat-eating critics who deny any equivalence.

I make it clear in this post that I don't deny the equivalence, and don't think that very young children have the moral worth of cognitively developed humans. (The optimal legality of Doing Bad Things to them is a slightly more complicated matter.)

we don't regard, say, humans with infantile Tay-Sachs who lack the potential to become cognitively mature adults as any less worthy of love, care and respect than heathy toddlers.

Well, I certainly do.

Apt comparison or otherwise, creating nonhuman-animal-friendly intelligence is going to be an immense challenge.

Eh...? Expand on this, please; I'm quite unsure what you mean here.

Stuart Rachels, Vegetarianism, in The Oxford Handbook of Animal Ethics, Oxford: Oxford University Press, 2012, pp. 877–905.

So, I've just finished reading this one.

To say that I found it unconvincing would be quite the understatement.

For one, Rachels seems entirely unwilling to even take seriously any objections to his moral premises or argument (he, again, takes the idea that we should care about animal suffering as given). He dismisses the strongest and most interesting objections outright; he selects the weakest objections to rebut, and condescendingly adds that "Resistance to [such] arguments usually stems from emotion, not reason. ... Moreover, they [opponents of his argument] want to justify their next hamburger."

Rachels then launches into a laundry list of other arguments against eating factory farmed animals, not based on a moral concern for animals. It seems that factory farming is bad in literally every way! It's bad for animals, it's bad for people, it causes diseases, eating meat is bad for our health, and more, and more.

(I'm always wary of such claims. When someone tells you thing A has bad effect X, you listen with concern; when they add that oh yeah, it also had bad effect Y! And Z! And W! ... and then you discover that their political/ideological alignment is "opponent of thing A"... suspicion creeps in. Can eating meat really just be universally bad, bad in every way, irredeemably bad so as to be completely unmotivated? Well, there's no law of nature that says that can't be the case (e.g. eating uranium probably has no upside), but I'm inclined to treat such claims with skepticism, and, in any case, I'd prefer each aspect of meat-eating to be argued against separately, such that I can evaluate them individually, not be faced with a shotgun barrage of everything at once.)

Incidentally, I find the "factory farming is detrimental to local human populations" argument much more convincing than any of the others, certainly far more so than the animal-suffering argument. If the provided facts are accurate, then that's the most salient case for stopping the practice — or, preferably, reforming it so as to mitigate the environmental and public-health impact.

I assign the "eating meat is bad for you" argument negligible weight. The one universal truth I've observed about nutrition claims is that finding someone else who's making the opposite claim is trivial. (The corollary is that generalizing nutritional findings to all humans in all circumstances is nigh-impossible.) Red meat reduces lifespan? But the peoples of the Caucasus highlands eat almost nothing but red meat, and they've got some of the longest lifespans in the world. The citations in this section, incidentally, amount to "page so-and-so of some book" and "a study". I can find "a study" that proves pretty much any nutritional claim. Thumbs down. (Vegetarians should really stay away from human-health arguments. It never makes them look good.)

Of the rest of the arguments Rachels makes, I found "industrial farming is worse than the Holocaust" (yes, he really claims this, making it clear that he means it) particularly ludicrous. Obviously, this argument is made with the express intent of being provocative; but as it does seem that Rachels genuinely believe it to be true, I can't help but conclude that here is a person who is exemplifying one of the most egregious failure modes of naive utilitarianism. (How many chickens would I sacrifice to save my great-grandfather from the Nazis? N, where N is any number. This seems to argue either for rejecting straightforward aggregation of value or for assigning chickens a value of 0.)