“True knowledge never shuts the door on more knowledge, but zeal often does.”

“Knowledge can be heady stuff, but it easily leads to an excess of zeal! -- to illusions of grandeur and a desire to impress others and achieve eminence . . . Our search for knowledge should be ceaseless, which means that it is open-ended, never resting on laurels, degrees, or past achievements.”

“As knowledge increases, the verdict of yesterday must be reversed today, and in the long run the most positive authority is the least to be trusted.”

“No matter where we begin, if we pursue knowledge diligently and honestly, our quest will inevitably lead us from the things of the earth to the things of heaven.”

“Things that appear unlikely, impossible, or paradoxical from one point of view often make perfectly good sense from another.”

“Doctors and trainers often see perfectly developed bodies, but nobody can even begin to imagine what a perfect *mind* would be like; that is where the whole range of progress and growth must take place.”

“In the business of scholarship, evidence is far more flexible than opinion. The prevailing view of the past is controlled not by evidence but by opinion.”