The collected works of John Stuart Mill

[A] feeling of liking or aversion to an action, confined to an individual, would have no chance of being accepted as a reason. The appeal is always to something which is assumed to belong to all mankind. But it is not of much consequence whether the feeling which is set up as its own standard is the feling of an individual human being, or of a multitude. A feeling is not proved to be right, and exempted from the necessity of justifying itself, because the writer or speaker is not only conscious of it in himself, but expects to find in other people, because instead of saying “I,” he says “you and I.”

Aim at something great; aim at things which are difficult; and there is no great thing which is not difficult. Do not pare down your undertaking to what you can hope to see successful in the next few years, or in the years of your own life. Fear not the reproach of Quixotism and impracticability, or to be pointed at as the knight-errants of an idea. After you have well weighed what you undertake, if you see your way clearly, and are convinced that you are right, go forward, even though you […] do it at the risk of being torn to pieces by the very men through whose changed hearts your purpose will one day be accomplished. Fight on with all your strength against whatever odds, and with however small a band of supporters. If you are right, the time will come when that small band will swell into a multitude: you will at least lay the foundations of something memorable, and you may […]—though you ought not to need or expect so great a reward—be spared to see that work completed which, when you began it, you only hoped it might be given to you to help forward a few stages on its way.

It is not human life only, not human life as such, that ought to be sacred to us, but human feelings. The human capacity of suffering is what we should cause to be respected, not the mere capacity of existing.