Exploration is really the essence of the human spirit.

Exploration really is the essence of the human spirit, and to pause, to falter, to turn our back on the quest for knowledge, is to perish.

America is the spirit of human exploration distilled.

Surefire things are deadening to the human spirit.

Enjoyment is an incredible energizer to the human spirit.

The human spirit cannot be seen; neither can it be denied.