IV. What are the Ends which are also Duties?

They are: A. OUR OWN PERFECTION, B. HAPPINESS OF OTHERS.

We cannot invert¹ 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 virtue² of the impulse of their nature), but this end cannot without contradiction be regarded as a duty. What a man of himself inevitably³ wills does not come under the notion of duty, for this is a constraint⁴ 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.

1 invert   

vt.使反转，使颠倒，使转化

参考例句：

• She catch the insect by invert her cup over it.她把杯子倒扣在昆虫上，将它逮住了。
• Invert the cake onto a cooling rack.把蛋糕倒扣在冷却架上。

2 virtue   

n.德行，美德；贞操；优点；功效，效力

参考例句：

• He was considered to be a paragon of virtue.他被认为是品德尽善尽美的典范。
• You need to decorate your mind with virtue.你应该用德行美化心灵。

3 inevitably   

adv.不可避免地；必然发生地

参考例句：

• In the way you go on,you are inevitably coming apart.照你们这样下去，毫无疑问是会散伙的。
• Technological changes will inevitably lead to unemployment.技术变革必然会导致失业。

4 constraint   

n.(on)约束，限制；限制(或约束)性的事物

参考例句：

• The boy felt constraint in her presence.那男孩在她面前感到局促不安。
• The lack of capital is major constraint on activities in the informal sector.资本短缺也是影响非正规部门生产经营的一个重要制约因素。