Moral patients are things towards which moral agents can have moral responsibilities. On this definition, all moral agents are also moral patients, but moral patients need not be moral agents. Only moral agents can function as the bearers of moral obligations towards others, while moral patients can be the objects of the moral obligations of others, but need not themselves be capable of moral agency.
We generally think of other adult human beings as moral agents, even though some adult human beings lack the effective capacity for moral agency, for instance, persons in comas. To qualify as a moral agent, one must satisfy the criteria generally accepted for mental competence as required for ascriptions of moral responsibility in the sense of liability for moral blame or praise. The actions of moral agents can be evaluated morally as to their blame or praiseworthiness, but not, for instance, the actions of infants and most animals. Nonhuman animals because they lack an effective capacity for moral agency can be readily classified as moral patients.
Thus, a moral patient does not have to be a moral agent or person, but could, for instance, also be nonhuman animals or an entire species, plants, microorganisms, an ecosystem, or even perhaps an inanimate object such as a work of art or a prized possession. The category of moral patients might be quite large and quite differentiated. It will need to be defined further.
Some kinds of moral patients are also agents, just not moral agents. In using the terms 'agent' and 'patient' I do not mean to imply that moral patients lack agency in their own right, or that moral agents cannot also be acted upon by moral patients. A shark, which is a moral patient can kill a man. A human infant, which is another kind of moral patient, can evoke in most human adults a caring impulse. Moral agents act upon moral patients and vice versa. In order to be considered a moral patient, that is, as the object of a moral responsibility, an entity must have some kind and degree of moral status.
As Francis Kamm has noted, there is a broad sense of moral status in which the concept can be defined as "what it is permissible or impermissible to do to some entity. In this sense, rocks may have the moral status of entities to which, just considering them, it is morally permissible to do anything" (F. M. Kamm. Intricate Ethics: Rights, Responsibilities, and Permissible Harm. Oxford: Oxford University Press, 2007, p. 227). But we normally use the term in a narrower sense as a contrast between "entities that in some important sense 'count' morally in their own right, and so are said to have moral status, and others that do not count morally in their own right." I will employ the term "moral standing" to denote things which count morally in their own rights either because of their intrinsic properties or relational properties. Having moral standing is a kind of moral status; other things like ordinary rocks do not have moral standing because they have the moral status of things to which we can do anything we please. Some other things which we cannot affect at all by means of human action have a different kind of moral status. The planet Jupiter or the Carina Nebula would fall into this category and would also lack moral standing.
Kamm endorses a suggestion by Christine Korsgaard that entities do not have to be considered to have an intrinsic value in order to have moral status in this sense; they only need to be considered as ends in the sense that some aspect of their good can "provide a reason (even if an overrideable one) for attitudes and actions independent of other considerations" (228). For instance, Kamm says, "A work of art or a tree may count in its own right in the sense that it gives us reason to constrain our behavior toward it (for example, not destroy it) just because that would preserve this entity" (228).
But Kamm further distinguishes doing something to an entity "for its own sake and not just in its own right." For Kamm only entities that have the capacity for sentience or consciousness can qualify as objects for whose sakes we can have moral obligations. I agree that entities which have the psychological capacities necessary for sentience have moral standing and are therefore moral patients. But I disagree with Kamm and also believe that there are organisms which are not sentient towards which we can act morally in their own rights even though they do not have interests in the psychological sense. All of those living things whose well-being can be affected for better or worse by the actions of moral agents can, on this view, be considered to have some kind or degree of moral standing and can therefore function as moral patients within the vulnerability relation.
To clarify the notion of moral status further, Kamm argues that, "there is a difference between one's having a duty to do something and having a duty to a specific entity to do it" (230). When we have a duty to someone, it typically creates a "correlative right or claim had by the entity to which the duty is owed against the person who owes it." We say that we act wrongly when we fail to fulfill a duty or responsibility to do something, but we say that we have wronged someone when we fail to fulfill our duty towards them as a right-holder. The party to whom a moral obligation is owed (its addressee) is not necessarily the party who is benefited or affected by that obligation (its object). This can be made clear by means of an example or two.
Suppose that Sam has mother, Judith, who has had a stroke which left her severely incapacitated and in need of care. But Sam has a job and a young family to care for as well, so he hires Gwen, a professional nurse, who promises Sam to take care of Sam's mother Judith while he is at work. In this example, Sam has a moral responsibility to care for his mother when she is vulnerable and depending upon him for her care, but he can delegate this responsibility to another caregiver who then enters in as a party to this moral relationship.
In this triangular moral relationship Gwen is a duty-bearer; she has a duty to Sam to take care of his mother Judith. Sam is the right-holder and the addressee of Gwen's duty since it is Sam who would be wronged by Gwen if she failed to properly discharge her duties. Judith is an object and beneficiary of Gwen's duty. Judith is in this case is a moral patient who is also a moral agent but who functions as the indirect object of Gwen's moral obligations. Sam functions as the direct object of Gwen's responsibility because she owes her duty to Sam. While Gwen owes her duty to Sam, because of her promise was addressed to him, Judith is the object of Gwen's duty because Gwen now has a responsibility to care for Judith that was delegated to her by Sam. On this account, Sam has a right against Gwen, and Gwen has a duty she owes to Sam, but Gwen also has a moral responsibility towards Judith who is the object and the beneficiary of her care. Judith is the object of Gwen's duties, but Sam is the right-holder who is in a position to demand that Gwen fulfill her responsibilities.
This is an example of how moral patients can function as the objects of a moral agent's obligations although they are not themselves are not right-holders in the relevant sense. Thus, a moral patient can be the object of the moral responsibilities of others without having rights against them.
One can drive this point home more forcefully by substituting something that is not a human being for Judith. Suppose we vary the case and stipulate that Sam asked Gwen to water his plants while he was away on vacation. Sam's plants are not moral agents, nor are they sentient, and are not the kind of things that can have rights. But Gwen still has a duty towards the plants because of the promise she has given to Sam. Sam has rights against Gwen, but Sam's plants don't.
Or consider the case in which Sam asks Gwen to take care of his 1200cc Harley Davidson motorcycle for him, say to change its oil and polish its chrome. In this case we would say that Gwen has a responsibility concerning Sam's Harley, but many people would be disinclined to say that the motorcycle is the object her responsibilities. Sam is still the addressee of Gwen's duties and he would be wronged if she does not do as she has promised. But motorcycles, and most other inanimate, non-living material artifacts, are not normally considered to be things that we can have obligations towards. In such cases, I will say that the object in question has a derived, or observer-relative kind of moral status. Its status is derived from the interests of moral patients who have "goods of their own" or can be regarded as "ends in themselves," but the object of the obligation, its beneficiary, itself cannot.
There can also be cases where a single entity, for example, another person, functions both as the object or beneficiary and the right-older with respect to someone else's duties. When rights ground moral responsibilities, for example, a duty, to refrain from torturing another person by subjecting them to electrical shocks, my duty corresponds to a right on her part not to be tortured. Here the object of my responsibilities and their beneficiary are the same individual. Rights ground moral duties that are in the interest of the right-holders. If I commit torture I both harm the person I torture and I wrong him because I have violated a right which he has against me.
However, when we have moral responsibilities concerning moral patients who are not also moral agents, no such rights are involved. So, for example, I may have a duty not to destroy a tree without good reason because the tree has a moral status, which (other things being equal), gives me reason not to destroy it. But this moral duty does not correlate with right on the part of the tree, and I will not have wronged the tree if I destroy it, although I may still have done something wrong. Trees and other kinds of living things can be moral patients that function as the objects of the moral responsibilities of moral agents without their also qualifying as right-holders.
Moral agents can have moral responsibilities that are other-regarding towards (or concerning) both other moral agents and towards various categories of moral patients having intrinsic and derived moral status. Moral agents can also have self-regarding moral responsibilities, that is, persons have can have moral responsibilities to themselves. Moral patients are, in general, things which are valuable and vulnerable to human action in a variety of different ways. Things which cannot be affected for good or for ill by human actions cannot be considered to be moral patients at all. The planet Jupiter, for instance, which is only a great gaseous sphere in space, is something which cannot be a moral patient because we cannot affect it in any way that might be considered as mattering to its "good" or "well-being." The limits of human action also mark the outer limits of possible human responsibilities.
We cannot have moral responsibilities concerning those things whose well-being we cannot affect through our action or inaction. We can't really do anything to Jupiter even though we have now shot satellites into it to try to learn more about it. But this action did not harm Jupiter in any way. Jupiter is, in fact, not even the sort of thing which can be harmed. We can only harm those things which can be thought of as having a well-being or a good of their own. The planet Jupiter has no good of its own, and even if it did, its good could not be affected in any way by human action, which is just another way of saying that things like the planet Jupiter cannot be moral patients.
However, I think that we can have moral responsibilities concerning the Earth, since we can affect the earth for good or ill by our actions. Unlike Jupiter, the Earth has a moral status of its own which derives from its being a living planet – a place in the cosmos where the phenomenon of life has emerged. Perhaps there are other planets in the universe where life has arisen. Personally, I believe that Earth cannot be the only site of life in the cosmos, but at this stage in humanity's scientific understanding of the universe we don't know this. However, we do know that life exists on Earth and that this fact makes Earth rather special. On the bio-centric view of moral value I will develop shortly, life is the basis of intrinsic value.