Nietzsche's treatise "On The Genealogy of Morals" is at once history, deconstruction and critique. Nietzsche's goal was to uncover the mystery of how morality came into existence. He believed that in doing do, he would lay bare the essential worthlessness of morality itself.
Nietzsche critiqued both reason and faith as aspects of man's depraved collective morality. His levied his critique in the name of the will to power, the human trait that he believed to be man's "one true virtue." The desire and drive to experience power -- to change one's own environment and circumstance -- was to Nietzsche the very foundation of a virtuous life. He critiqued social morality and faith because he saw them as limiting man's will to power. He argued that these social constructs were incompatible with true virtue.
Nietzsche believed that morality was borne out of the resentment that weaker, oppressed individuals harbored toward their oppressors. He couched the origins of the good vs. evil dichotomy in a religious narrative history of struggle between Rome and Judea. Nietzsche argued that Judeo-Christian concepts of good and evil reflected nothing more than resentment of an enslaved people toward their captors. He labeled this resentment "slave morality."