The essence of life is doing things for their own sakes.

A process which led from the amoeba to man appeared to the philosophers to be obviously a progress though whether the amoeba would agree with this opinion is not known.

As for earthquakes, though they were still formidable, they were so interesting that men of science could hardly regret them.

So far I have been speaking of theoretical science, which is an attempt to understand the world. Practical science, which is an attempt to change the world, has been important from the first, and has continually increased in importance, until it has almost ousted theoretical science from men's thoughts.

The puritanism of Christianity has played havoc with the moderation that an enlightened and tolerant critical spirit would have produced. I've noticed that in whatever country, county, town, or other region there is a regulation enjoining temperance, the population seems to be entirely composed of teetotallers and drunkards. There's a Bible on that shelf there. But I keep it next to Voltaire - poison and antidote.

I feel life is so small unless it has windows into other worlds.

Italy, and the spring and first love all together should suffice to make the gloomiest person happy.