The moral power of law commanding obedience. Obligation is moral necessity, imposed on a free will, thus differing from physical necessity, which controls nonfree beings. Moral necessity arises from the final cause, which is from an end or good known by the intellect. This good, perceived by the mind, moves the will either to arouse or to restrain it. Since there is only one way to achieve one's last end, namely by morally good actions, a person is obliged to live what conscience tells him or her is the good life.