“The true roll in determing to embrace or reject anything is not whether it have any evil in it but whether it have more of evil than of good. There are few things wholly evil or wholly good.”

Source: Lady Midnight

Address at the Conference on Cosmic Design, American Association for the Advancement of Science, Washington, D.C. (April 1999)
This comment is modified in a later article derived from these talks:
:Frederick Douglass told in his Narrative how his condition as a slave became worse when his master underwent a religious conversion that allowed him to justify slavery as the punishment of the children of Ham. Mark Twain described his mother as a genuinely good person, whose soft heart pitied even Satan, but who had no doubt about the legitimacy of slavery, because in years of living in antebellum Missouri she had never heard any sermon opposing slavery, but only countless sermons preaching that slavery was God's will. With or without religion, good people can behave well and bad people can do evil; but for good people to do evil — that takes religion.
:* "A Designer Universe?" at PhysLink.com http://www.physlink.com/Education/essay_weinberg.cfm

The Virtue of Selfishness (1964)

Case of John Lambert and others (1793), 22 How. St. Tr. 1018.

A Vindication of Natural Society (1756)
Context: We scarce ever had a prince, who by fraud, or violence, had not made some infringement on the constitution. We scarce ever had a parliament which knew, when it attempted to set limits to the royal authority, how to set limits to its own. Evils we have had continually calling for reformation, and reformations more grievous than any evils. Our boasted liberty sometimes trodden down, sometimes giddily set up, and ever precariously fluctuating and unsettled; it has only been kept alive by the blasts of continual feuds, wars, and conspiracies.

Let the Great World Spin (2009), Book One: A Fear of Love

Source: An Introduction to the Principles of Morals and Legislation (1789; 1823), Ch. 10: Of Motives