There is no disinfectant like success.

If our knowledge is, as I believe, only an island in an infinite sea of ignorance, how can we in our short lifetime find satisfaction in exploring our little island? How can we persuade ourselves to be exhilarated by our meager knowledge and yet not be discouraged by the ocean vistas?

The most promising words ever written on the maps of human knowledge are terra incognita, unknown territory.

Knowledge is not simply another commodity. On the contrary. Knowledge is never used up. It increases by diffusion and grows by dispersion.

Disagreement produces debate but dissent produces dissension.

Our American past always speaks to us with two voices: the voice of the past, and the voice of the present. We are always asking two quite different questions. Historians reading the words of John Winthrop usually ask, What did they mean to him? Citizens ask, What do they mean to us? Historians are trained to seek the original meaning; all of us want to know the present meaning.

We suffer primarily not from our vices or our weaknesses, but from our illusions. We are haunted, not by reality, but by those images we have put in their place.