A mind of its own

(It) has intelligence of itself, & although the will of the man desires to stimulate it, it remains obstinate & takes its own course, and moving sometimes of itself without license or thought by the man, whether he be sleeping, or waking, it does what it desires; & often the man is asleep & it is awake, & many times the man is awake, and it is asleep.” ---Leonardo da Vinci