We suffer equal pain from the pertinacious adhesion of unwelcome images, as from the evanescence of those which are pleasing and useful.

When emulation leads us to strive for self-elevation by merit alone, and not by belittling another, then it is one of the grandest possible incentives to action.

Sleep is a state in which a great part of every life is passed. No animal has yet been discovered, whose existence is not varied with intervals of insensibility; and some late philosophers have extended the empire of sleep over the vegetable world.

The most fatal disease of friendship is gradual decay.

Of all kinds of credulity, the most obstinate is that of party-spirit; of men, who, being numbered, they know not why, in any party, resign the use of their own eyes and ears, and resolve to believe nothing that does not favor those whom they profess to follow.

Smoking is a shocking thing - blowing smoke out of our mouths into other people's mouths, eyes, and noses, and having the same thing done to us.

He that can swim needs not despair to fly; to swim is to fly in a grosser fluid, and to fly is to swim in a subtler. We are only to proportion our power of resistance to the different density of matter through which we are to pass. You will be necessarily upborne by the air if you can renew any impulse upon it faster than the air can recede from the pressure.