“Just as the brain stimulates and maintains the other tissues, and each hemisphere has a trophic, stimulating effect on the other, the older, instinctive systems of the brain activate the cortex, and exert a trophic, growth-promoting influence on it. Wild animals have larger brains than caged ones, which implies that life and freedom are brain stimulants. Problems are opportunities. People can be the richest kind of opportunity, the most stimulating kind of problem. To do this they have to arouse tension. (Blake said ‘opposition is true friendship.’) This is not to advocate competition. Competition tries to eliminate the problem by defeating an opponent, and can exist only in the armored character, which allows energy to flow only in one direction, and which can’t tolerate tension. (An opponent-friend is one who ‘inspires’ you, who makes you gasp for breath and resolution.)”