Thank you for the thoughtful comment! It is an excellent book – if you are at all interested in Kant's moral philosophy, I highly recommend it. I will preface the remainder of this comment with the caveat that I am explaining someone else's work, and that Professor Korsgaard may not agree with my interpretation. Also, any typos in the quoted passages are copying errors.

I haven't read her work myself and probably should, but I was told by someone that basically condition 3 or even having goal-directed behaviour is not necessary. I would hope it wouldn't be, because we could have a being who experiences good and bad and so has their own ends, but has no power to control what they experience and so would just be completely vulnerable and unable to pursue their own ends. Wouldn't such a being still matter?

Here's a passage from the book that expands on that thought but doesn't counter your objection:

The small [objection] is that the definition that I have given of what an animal is is not the same as the definition a contemporary biologist would give. An "animal", as I am using the term, is an organism that functions as an agent, where by agency I mean something like representation-governed locomotion. Animals are conscious organisms who seek out the things that are (functionally) good-for them and try to avoid the things that are bad. [...] The organisms we are concerned with when we think about whether we have duties to animals are sentient beings who perceive the world in valenced ways and act accordingly. This is the feature of organic life that I have argued places an organism in the morally interesting category of having a final good.

However, later on she gets to the argument from marginal cases (if something like intelligence or rationality is the ground for moral standing among humans, then what about infants, or folks with severe developmental impairments?), which I think is similar to your objection here. Korsgaard argues against it, because to her, there is such a thing as a type of creature, even if categories have fuzzy borders. And though your example beings may not be able to pursue their own functional goods, they are still the sorts of creatures who do.

A human infant is not a particular kind of creature, but a human creature at a particular life stage. I believe that it is not proper to assign moral standing, and the properties on which it is grounded, to life stages or to the subjects of those stages. Moral standing should be accorded to persons and animals considered as the subjects of their whole lives, at least in the case of animals with enough psychic unity over time to be regarded as the subjects of their whole life. Nor, except perhaps in the case of extremely simple life forms, should we think of the subject of a life merely as a collection of the subjects of the different temporal stages of the life. [F]or most animals having a self is not just a matter of being conscious at any given moment, but rather a matter of having a consciousness or a point of view that is functionally unified both at a particular time and from one moment to the next. That ongoing self is the thing that should have or lack moral standing, or be the proper unit of moral concern.

[...]

There is a third reason for rejecting the argument from marginal cases, and it is the most important. A creature is not just a collection of properties, but a functional unity, whose parts and systems work together in keeping him alive and healthy in the particular way that is characteristic to his kind. Even if it were correct to characterize a human being with cognitive defects as "lacking reason", which usually it is not, this would not mean that it was appropriate to treat the human being as a non-rational animal. Rationality is not just a property that you might have or lack without any other difference, like blue eyes. To say that a creature is rational is not just to say that he has "reason" as one of his many properties, but to say something about the way he functions. [...] A rational being who lacks some of the properties that together make rational functioning possible is not non-rational, but rather defectively rational, and therefore unable to function well. [...] It is not as if you could simply subtract "rationality" from a human animal. A non-rational animal, after all, functions perfectly well without understanding the principles of reason, since he makes his choices in a different way.

[...]

The Argument from Marginal Cases ignores the functional unity of creatures. A creature who is constructed to function in part by reasoning but who is still developing or has been damaged is still a rational creature. So the Kantian need not grant and should not grant that infants, the insane, the demented, and so on, are non-rational beings. The point is not, of course, that we should treat infants and people with cognitive disabilities exactly the way we treat adult rational beings, because they too are rational beings. The way we treat any creature has to be responsive to the creature's actual condition. But the creature's condition itself is not given by a list of properties, but also by the way those properties work together.

Korsgaard is talking about rationality here because that, to her, is what sets humans apart from the other animals (though of course she thinks that is the reason why we are moral agents, but not why we have moral standing). But I think she would argue similarly about creatures that are defective in other ways, e.g. who has no power to control what they experience or to pursue goals.

I also wonder what she has in mind by "functional" in "functional good". Do we need to decide what something's function is, if any, to define their goods and bads, and how do we do that? In my view, animals define their own goods and bads through their valenced experiences and/or desires, not just that they happen to experience their goods and bads or that their experiences guide them towards their own functional goods.

If I understand you correctly, I think she would agree. Her distinction between "final goods" and "functional goods" comes, I think, from this 1983 paper of hers, though there she calls functional goods "instrumental" instead. The functional good is basically that which allows a thing to function well, e.g. a whetstone is good for the blade because it keeps it sharp and tar is good for the boat because it keeps it from taking in water. The final good is "the end or aim of all our strivings, or at any rate the crown of their success, the summum bonum, a state of affairs that is desirable or valuable or worth achieving for its own sake". Where does the final good come from? Korsgaard basically argues, if I recall correctly, following Aristotle, that creatures have functions, and that, when we act to achieve some end, to attain whatever we value as good-for us, we take that end to be good in the final sense. I think this is pretty similar to what you were getting at?

It's interesting that she brings up artwork and the environment, too, as potential ends in themselves.

Ah yes, I thought so too, especially since I had understood (mistakenly, apparently) from the book that she did not think of those things as ends in themselves. I actually wrote a dialogue in the old style about this very subject, concluding that inanimate objects are not ends in themselves.

Indeed, and a commenter there pointed out an interesting paper by Richard Yetter Chappell (pdf) which explores and argues against this claim by Korsgaard:

In utilitarianism, people and animals don’t really matter at all; they are just the place where the valuable things happen.

The title of the paper is "Value Receptacles". I haven't read it yet but I suspect it would be of interest to many here.

That's interesting and I think that's true to a certain extent, the bottomless pits of suffering and all that. Though Kantianism does make some pretty strong demands in its own way, for instance in the way that it really hammers home the idea of seeing things from others' points of view (via the Formula of Humanity), or in the way that it considers some duties to be absolute ("perfect").

I believe that Korsgaard also thinks we have duties to help others' promote their own good if it's at no great cost to ourselves, though these duties are not as strong as those not to violate other people's autonomy. I think maybe these sorts of duties lead to something like Effective Altruism, though I haven't really thought all of this through yet, or read much of the relevant literature, so what do I know.

Only seeing this now, but she does have sections in the book on thinking about species, habitat loss, eliminating predation and what she calls "creation ethics" among other things. I didn't get the feeling reading the book that she would be against welfare reform, but leafing through the pages now I couldn't find any passage that covers that topic explicitly. Thanks for the resources.