We too often go through life stumbling blindly forward in the mundane haze of existence day passing after day. But in order to live, above merely existing, we must live justly and well. This is what ethics allows us to attempt. This attempt is made more rationally when we know from whence ethics comes. This question is both one of the authority of morality and its history.
Examining the Hobbesian social contract theory and the Christian will of God theory provide a different insight into the origin of ethics than simply studying the history of ethics. This is accomplished in two ways. First, focusing on the authority of morality allows us to answer questions about morality regarding why we should obey ethical rules in the present. Second, this focus forces us to imagine a future in which these moral values have ceased to exist. Would the future be better or worse? Simply studying the history of ethics gives us a window into the past but does not necessarily focus on the present or future.
The study of the ethical authority of Thomas Hobbes' Social Contract Theory and Christianity allows us to focus on the present and the future. Hobbes postulated a social contract that regarded Man as a power hungry, selfish being grappling with anyone in his way, subject to his animal passions. Christianity postulates that Man is made in the image of God. These two views provide us with the obligations and duties that guide our actions. But if their assumptions regarding the authority of ethics, namely a social contract or our God Soul, are wrong then those obligations and duties will be an ethics not commensurate with human nature and therefore unsustainable.
Our ethical principles are not rooted in any mythical "social past" or irrational notion of a Logos, or God as the progenitor of humanity. Our ethical principles are rooted in our natural animal dispositions. When these natural dispositions are coupled with human reason then our ethical principles are formed and the authority upon which they rest is established.
ok, back to my old fashioned metaphysical Lockean, Burkean self. :)