The mind of the scholar, if you would have it large and liberal, should come in contact with other minds. It is better that his armor should be somewhat bruised by rude encounters even, than hang forever rusting on the wall.
My praise shall be dedicated to the mind itself. The mind is the man, and the knowledge is the mind. A man is but what he knoweth. The mind is but an accident to knowledge, for knowledge is the double of that which is.
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 than a much smaller amount if you have not thought it over for yourself.
It is commonly observed that a sudden wealth, like a prize drawn in a lottery or a large bequest to a poor family, does not permanently enrich. They have served no apprenticeship to wealth, and with the rapid wealth come rapid claims which they do not know how to deny, and the treasure is quickly dissipated.
Thoughts without content are empty, intuitions without concepts are blind... The understanding can intuit nothing, the senses can think nothing. Only through their union can knowledge arise.
Go out of the house to see the moon, and 't is mere tinsel; it will not please as when its light shines upon your necessary journey. The beauty that shimmers in the yellow afternoons of October, who could ever clutch it? Go forth to find it, and it is gone: 't is only a mirage as you look from the windows of diligence.
It is an infantile superstition of the human spirit that virginity would be thought a virtue and not the barrier that separates ignorance from knowledge.
Nobody knows how the stand of our knowledge about the atom would be without him. Personally, [Niels] Bohr is one of the amiable colleagues I have met. He utters his opinions like one perpetually groping and never like one who believes himself to be in possession of the truth.