Irons rusts from disuse, stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind. – Leonardo da Vinci, Notebooks, 1508
Those who believe that they believe in God, but without passion in their hearts, without anguish in mind, without uncertainty, without doubt, without an element of despair even in their consolation, believe in the God idea, not God himself. – Miguel de Unamuno
