If possessing a higher degree of intelligence does not entitle one human to use another for his or her own ends, how can it entitle humans to exploit non-humans?

In a situation where many national leaders do the same thing and look out for national interests, and with an issue like global warming, you're likely to get no solution, so I think you have to have some kind of ethical trump on some of those issues.

At the descriptive level, certainly, you would expect different cultures to develop different sorts of ethics and obviously they have; that doesn't mean that you can't think of overarching ethical principles you would want people to follow in all kinds of places.

There is no humane slaughter requirement for wild fish caught and killed at sea, nor, in most places, for farmed fish.

We have a new generation of very rich people who want to do more with their money than buy a lot of expensive toys. They want to live meaningful lives.

As for cages themselves, an ordinary citizen who kept dogs in similar conditions for their entire lives would risk prosecution for cruelty. A pig producer who keeps an animal of comparable intelligence in this manner, however, is more likely to be rewarded with a tax concession or, in some countries, a direct government subsidy.

Effective altruism is the form of altruism in which we bring our rational capacities to bear in order to do the most good that we can.