The moment one asks himself whether he is happy, he ceases to be so.

In proportion to the development of his individuality, each person becomes more valuable to himself, and is therefore capable of being more valuable to others. . . .

A [psychological] difficulty is not an impossibility.

Not only the grounds of the opinion are forgotten in the absence of discussion, but too often the meaning of the opinion itself... Instead of a vivid conception and a living belief, there remain only a few phrases retained by rote; or, if any part, the shell and husk only of the meaning is retained, the finer essence being lost.

It is questionable if all the mechanical inventions yet made have lightened the day's toil of any human being.

So true is that unnatural generally means only uncustomary, and that everything which is usual appears natural.

When one's ideas are not challenged, one's ability to defend them weakens.