What people commonly call Fate is, as a general rule, nothing but their own stupid and foolish conduct.

As the biggest library if it is in disorder is not as useful as a small but well-arranged one, so you may accumulate a vast amount of knowledge but it will be of far less value to you than a much smaller amount if you have not thought it over for yourself; because only through ordering what you know by comparing every truth with every other truth can you take complete possession of your knowledge and get it into your power. You can think about only what you know, so you ought to learn something; on the other hand, you can know only what you have thought about.

If there is anything in the world that can really be called a man's property, it is surely that which is the result of his mental activity.

Every child is in a way a genius; and every genius is in a way a child.

When a new truth enters the world, the first stage of reaction to it is ridicule, the second stage is violent opposition, and in the third stage, that truth comes to be regarded as self-evident.

What now on the other hand makes people sociable is their incapacity to endure solitude and thus themselves.

If the lives of men were relieved of all need, hardship and adversity; if everything they took in hand were successful, they would be so swollen with arrogance that, though they might not burst, they would present the spectacle of unbridled folly-nay, they would go mad. And I may say, further, that a certain amount of care or pain or trouble is necessary for every man at all times. A ship without ballast is unstable and will not go straight.