Of all tools, an observatory is the most sublime. . . . What is so good in a college as an observatory? The sublime attaches to the door and to the first stair you ascent, that this is the road to the stars.

I am sure of this, that by going much alone a man will get more of a noble courage in thought and word than from all the wisdom that is in books.

I read your piece on Plato. Holmes, when you strike at a king, you must kill him.

The question is whether [suicide] is the way out, or the way in.

The soul is not born; it does not die; it was not produced from anyone… Unborn, eternal, it is not slain, though the body is slain.

Those who live to the future must always appear selfish to those who live to the present.

All things are moral. That soul, which within us is a sentiment, outside of us is a law. We feel its inspiration; out there in history we can see its fatal strength.