“Arguments can always be answered. Moral philosophy, unlike straight moralizing, arises from and trives on plurality of values.”

Act I, sc. i.
Tis Pity She's a Whore (1629-33?)

Source: Life, Sex, and Ideas: The Good Life Without God (2002), Chapter 2, “Moral Education” (p. 10)

The Doctrine Of Survival And Doctor Ethics (1992)

Trattato Terzo, Ch. 15.
Il Convivio (1304–1307)

Source: The Virtue of Selfishness: A New Concept of Egoism

Beast and Man: The Roots of Human Nature (1979).
Context: Do we find ourselves a species naturally free from conflict? We do not. There has not, apparently, been in our evolution a kind of rationalization which might seem a possible solution to problems of conflict--namely, a takeover by some major motive, such as the desire for future pleasure, which would automatically rule out all competing desires. Instead, what has developed is our intelligence. And this in some ways makes matters worse, since it shows us many desirable things that we would not otherwise have thought of, as well as the quite sufficient number we knew about for a start. In compensation, however, it does help us to arbitrate. Rules and principles, standards and ideals emerge as part of a priority system by which we guide ourselves through the jungle. They never make the job easy--desires that we put low on our priority system do not merely vanish--but they make it possible. And it is in working out these concepts more fully, in trying to extend their usefulness, that moral philosophy begins. Were there no conflict, it [moral philosophy] could never have arisen.

Grigby v. Oakes (1801), 1 Bos. & Pull. 528.

What Would You Substitute for the Bible as a Moral Guide? (1900)
Context: What then is, or can be called, a moral guide? The shortest possible answer is one word: Intelligence. We want the experience of mankind, the true history of the race. We want the history of intellectual development, of the growth of the ethical, of the idea of justice, of conscience, of charity, of self-denial. We want to know the paths and roads that have been traveled by the human mind. These facts in general, these histories in outline, the results reached, the conclusions formed, the principles evolved, taken together, would form the best conceivable moral guide. We cannot depend on what are called “inspired books,” or the religions of the world. These religions are based on the supernatural, and according to them we are under obligation to worship and obey some supernatural being, or beings. All these religions are inconsistent with intellectual liberty. They are the enemies of thought, of investigation, of mental honesty. They destroy the manliness of man. They promise eternal rewards for belief, for credulity, for what they call faith. This is not only absurd, but it is immoral.