They are: A. OUR OWN PERFECTION, B. HAPPINESS OF OTHERS.
We cannot invert these and make on one side our own happiness, and on the other the perfection of others, ends which should be in themselves duties for the same person.
For one's own happiness is, no doubt, an end that all men have (by virtue of the impulse of their nature), but this end cannot without contradiction be regarded as a duty. What a man of himself inevitably wills does not come under the notion of duty, for this is a constraint to an end reluctantly adopted. It is, therefore, a contradiction to say that a man is in duty bound to advance his own happiness with all his power.
It is likewise a contradiction to make the perfection of another my end, and to regard myself as in duty bound to promote it. For it is just in this that the perfection of another man as a person consists, namely, that he is able of himself to set before him his own end according to his own notions of duty; and it is a contradiction to require (to make it a duty for me) that I should do something which no other but himself can do.