This is the question explored in my latest article (Tim Hayward, ‘On Prepositional Duties’, Ethics, 123.2 (2013): 264-291). We familiarly speak of a person having a duty ‘to’ another person, but are we really clear what this expression conveys? I suggest that what is clear is that different people understand quite different things by it. If we notice this, then we may also realise that there is more of a puzzle than often recognized about what is going on when the preposition to is tacked onto the noun duty. If reference to a duty indicates what you must do, then what has that to do with another person? The idea of having a duty ‘to’ a person is not like that of having a debt to a person, or making a promise to a person, for instance, because, unlike those ideas, duties can be specified without necessary reference to any second party – as simply what you ought to do. You can have such duties regardless of whether or not any other person has some stake in your doing what you ought; indeed, another person might have a stake in your doing something when it is what you ought not to do.
The general question first occurred to me when thinking about debates in animal ethics as to whether we have duties to animals (in this paper of 1994). It arose as a puzzle about a particular line of criticism directed against Immanuel Kant’s moral philosophy: Kant allowed that we have duties not to be cruel to animals, but Kant held that while this means, say, that Albert has a duty not to kick the dog, it does not mean Albert has a duty to the dog not to kick the dog. What I puzzled over is what difference it makes whether or not, given an acknowledged duty not to kick the dog, there is a duty to the dog not to kick the dog. Kant’s reasoning turns on how a dog differs from a person: not being a rational moral agent, a dog is not the kind of entity with whom an agent can have the kind of moral relationship that we characterize as a ‘duty to’. But if we apply Kant’s test, then a lot of our other familiar uses of the expression would be mistaken as well. Notoriously, mentally incapacitated humans, for instance, and maybe children too, would be in the same moral boat as Kant’s dogs.
So a competing idea is that we have a duty to another being – whether ‘rational’ or otherwise – when our action stands to do them some good or harm as measured by their own interests. This sort of view is captured in the moral philosophy of David Hume. Between Kant’s view and Hume’s there is a clear gulf: it is evident when they lead to identifying different persons in response to the question ‘whom is this duty a duty to?’
This divergence of views marks, too, the fault line between two influential accounts of how a right is implied by a ‘duty to’. (And this is the matter that revived my interest in the basic puzzle and prompted the present contribution to the Ethics Symposium on Rights and the Direction of Duties.) The two dominant kinds of account – those of the Will theory and the Interest theory of rights, in their various respective historical guises – have been in competition for centuries. Valiant attempts by some philosophers recently to bridge that divide have, I maintain, come unstuck from one side or the other, if not both. They have assumed that because we have the expression, some unified sense for it must be determinable. I suggest the assumption is wrong.
So this is one upshot – a rather theoretical one – of my argument: unless you are prepared to get into a tussle between Hume and Kant, and take a definite side in it, then you probably should refrain from using the expression at all! (And even if you are clear on your own philosophical assumptions, you should know that many others won’t share them – or in some cases even understand them – and so you might refrain out of simple good manners!) But then, you may well ask – and here we face a more practical concern – where would that leave you on such major and pressing ethical questions as what duties do we have to distant strangers, to the poor, to future generations, to nonhuman beings?
My response is that it leaves us exactly where we need to be, namely, recognizing that we are thinking about substantive moral ideas and human relationships. We are then able to do so without such distracting assumptions as that moral inquiry can be directed into a special kind of world in which there are things like ‘duties’ and ‘rights’ to be discovered and analysed. Those of us who philosophize about ethics can thereby be saved a lot of unnecessary confusion about the supposed ‘nature’ of a right, or a duty, or a duty to. We, in turn, can also then stop misleading people who want to engage ethically with the world when they look to philosophers for guidance.
So the argument is ultimately a cautionary one. I believe it is worth making because of the depth of confusion that abides in the literature that tries to delineate links between duties and rights. If even part of the confusion can be dispelled, it is worthwhile showing this. The other – and more ambitious – part of my task, which remains for another occasion, is to offer some clarifying arguments for those who theorise what rights ‘are’.