He who lets the world, or his own portion of it, choose his plan of life for him, has no need of any other faculty than the ape-like one of imitation. He who chooses his plan for himself, employs all his faculties. He must use observation to see, reasoning and judgment to foresee, activity to gather materials for decision, discrimination to decide, and when he has decided, firmness and self-control to hold to his deliberate decision.
The mental and moral, like the muscular powers, are improved only by being used.
You must know the big ideas in the big disciplines and use them routinely — all of them, not just a few.
The most dangerous worldview is the worldview of those who have not viewed the world.
They are ill discoverers that think there is no land, when they can see nothing but sea.