“It is the presence of doubt and the discovery of truth to answer that doubt that is the key to the whole process. Doubt is the key to spirituality, just as doubt is the key to science.”

“The key to wisdom is this -- constant and frequent questioning ... for by doubting we are led to question and by questioning we arrive at the truth.”

“Assiduous and frequent questioning is indeed the first key to wisdom... for by doubting we come to inquiry; through inquiring we perceive the truth...”

“Willpower is the key to success. Successful people strive no matter what they feel by applying their will to overcome apathy, doubt or fear.”

“Indeed, the idea that doubt can be heroic, if it is locked into a structure as grand as that of the paintings of Cezanne's old age, is one of the keys to our century. A touchstone of modernity itself.”

“Doubt thou the stars are fire;Doubt that the sun doth move;Doubt truth to be a liar;But never doubt I love.”

“Magic must have meaning to hold power. You must believe in yourmagic or it is useless. Focus is the key. Focus your mind and your spirit.You must have a strong will to do what you must. Doubt causes weakness.Weakness causes doubt. Fear cripples us. Believe in your power and youwill become powerful.”