Science is the topography of ignorance. From a few elevated points we triangulate vast spaces, inclosing infinite unknown details. We cast the lead, and draw up a little sand from abysses we may never reach with our dredges.

The root of joy, as of duty, is to put all one's powers towards some great end.

I find the great thing in this world is not so much where we stand, as in what direction we are moving: To reach the port of heaven, we must sail sometimes with the wind and sometimes against it, but we must sail, and not drift, nor lie at anchor.

Reason may be the lever, but sentiment gives you the fulcrum and the place to stand on if you want to move the world.

Life is an end in itself, and the only question as to whether it is worth living is whether you have had enough of it.

Most people have died before they expire; died to all earthly longings, so that the last breath is only, as it were, the locking of the door of the already deserted mansion.

Young men know the rules, but old men know the exceptions.