The doctrine that each of us has a special obligation to benefit himself as such, may be called Ethical Egoism; and the doctrine that each of us has a special obligation to benefit others, as such, may be called Ethical Altruism.
Now a plain consequence of [Henry] Sidgwick's second principle is that both these doctrines are false, and that what may be called Ethical Neutralism is true. Suppose that, on a certain occasion, a person would increase the balance of good over evil in the world more by benefiting another, at the cost of foregoing a benefit or inflicting an injury on himself, than by any other action then open to him. Then it would be his duty to do this. Suppose that, on a certain other occasion, a person could increase that balance more by benefiting himself, at the cost of withholding a benefit from another or inflicting an injury on him, than by any other action then open to him. Then it would be his duty to do that.
I will now consider in some detail these three alternative doctrines about self and others. The first point which I will make is that neither Ethical Egoism nor Ethical Altruism can be rejected in limine as involving an internal inconsistency. Each of these doctrines might be held in milder or more extreme forms. It will suffice if I take the most extreme form of each, and show that it is internally coherent.
The extreme form of Ethical Egoism might be stated as follows. Each person is under a direct obligation to benefit himself as such. He is under no direct obligation to benefit any other person, though he will be under an indirect obligation to do this so far and only so far as that is the most efficient means available to him for benefiting himself. He is forbidden to benefit another person, if doing so will in in the long run be detrimental to himself.
Now suppose that A is an Ethical Egoist of this extreme kind. He can admit that, if a certain experience or a certain disposition of his own would be intrinsically good, a precisely similar experience or disposition of B's would caeteris paribus be also and equally good, i.e. he can admit Sidgwick's first principle. But he will assert that his duty is not to produce good experiences and good dispositions as such, without regard to the question of who will have them. A has an obligation to produce good experiences and good dispositions in A, and no direct obligation to produce them in B or in anyone else. Similarly, B has an obligation to produce good experiences and good dispositions in B, and no direct obligation to produce then in A or anyone else. A can admit this about B, and B can admit it about A. Plainly there is no internal inconsistency in this doctrine. What it is inconsistent with is Sidgwick's principle that each of us has an unqualified obligation to maximize the balance of good over evil in the lives and personalities of all whom he can affect, and to pay no regard to the question which particular individuals or classes of individuals these goods and evils will occur in, except in so far as that may affect the balance.
(C. D. Broad, "Self and Others," Herbert Spencer Lecture, Oxford University, 1953)