"I had come to agree with Santayana that there is no such thing as ethical knowledge... I adopted as my guiding thought the principle that ethics is derived from passions and that there is no valid method of travelling from passion to what ought to be done. I adopted David Hume's maxim that 'Reason is, and ought only to be, the slave of the passions'. I am not satisfied with this, but it is the best that I can do... All that I can find to say on this subject is that an ethical opinion can only be defended by an ethical axiom, but, if the axiom is not accepted, there is no way of reaching a rational conclusion."