"He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast."

"The noblest pleasure is the joy of understanding."

"Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind."

"One can have no smaller or greater mastery than mastery of oneself."

"Necessity is the mistress and guide of nature."