“Happiness” translates the Greek word “eudaimonia,” but not very well. Eudaimonia is the ultimate goal of all human activity, what we live for. And that, essentially, is “the active life of reason” (says Aristotle). Dogs don’t live “the active life of reason,” so they don’t have eudaimonia, so (in translation) they can’t be happy. That doesn’t sound so strange.
But then, if they can’t be happy, in Aristotle’s high-flown sense, can’t they at least enjoy their lives? Or perhaps just flourish in their own particular way? It seems as if, just as it’s an excellent question what makes a person’s life go well or badly, there’s also a question what makes an animal’s life go well or badly. And Aristotle never directly or thoroughly addresses it (as far as I know).
It’s natural to suspect that he doesn’t because the subject of animals was beneath him. The problem with that interpretation is that he actually wrote lots and lots about animals. In fact, his works on animal life are more voluminous than his more famous works on metaphysics, logic, and ethics.
A student in my class made the very useful observation that Aristotle kicks off the whole subject of the human good with the idea that the good is our end or aim. Clarifying what it is is worthwhile, he says, because it can make us better “archers,” giving us a target to aim for.
Could this be the key to Aristotle’s failure to take up the topic of animal wellbeing? Animals don’t consciously aim for anything. Maybe that’s the heart of the matter, but then I think Aristotle has to be charged with a mistake. The mistake is in thinking that individuals can only have lives that go well or badly if they are “smart” enough to have conscious aims. It’s not true! (Think of someone who has a severe intellectual disability, for example.)
It’s really important to have a concept of what makes an animal’s life go well, because we humans have massive control over animal lives. Should you keep your cat inside or let him run wild (and risk an early death)? Is it wrong to declaw him? Is it wrong to keep birds in cages and dogs in crates? Are we harming veal calves, laying hens, and pregnant sows by giving them no space to move?
The good of animals is something that animals don’t (or possibly don't) consciously aim for themselves, but it’s something we could aim for, if we just had a clear idea what it is. It sounds mildly silly, but we need a good account of “the good life” for animals.