“What we can and should acknowledge is that there is a difference between moral confidence and moral certitude, and that in both moral and political matters there is always a place for prudence and humility, for the facts of the case and the particulars of the time. A conservatism that fails to account for these is no conservatism at all.”

Address on religious factions (1981)
Context: I must make it clear that I don't condemn these groups for what they believe. I happen to share many of the values emphasized by these organizations.
I'm frankly sick and tired of the political preachers across this country telling me as a citizen that if I want to be a moral person, I must believe in "A," "B," "C" and "D." Just who do they think they are? And from where do they presume to claim the right to dictate their moral beliefs to me?
And I am even more angry as a legislator who must endure the threats of every religious group who thinks it has some God-granted right to control my vote on every roll call in the Senate. I am warning them today: I will fight them every step of the way if they try to dictate their moral convictions to all Americans in the name of "conservatism." … This unrelenting obsession with a particular goal destroys the perspective of many decent people. They have become easy prey to manipulation and misjudgment.

Source: Treason of the Intellectuals (1927), p. 110

Six Principles of Political Realism, § 5.
Politics Among Nations (1948)
Context: Political realism refuses to identify the moral aspirations of a particular nation with the moral laws that govern the universe. As it distinguishes between truth and opinion, so it distinguishes between truth and idolatry. All nations are tempted — and few have been able to resist the power for long — to clothe their own aspirations and action in the moral purposes of the universe. To know that nations are subject to the moral law is one thing, while to pretend to know with certainty what is good and evil in the relations among nations is quite another. There is a world of difference between the belief that all nations stand under the judgment of God, inscrutable to the human mind, and the blasphemous conviction that God is always on one's side and that what one wills oneself cannot fail to be willed by God also.

Quoted in [Richard C. Reuben, Man in the Middle, California Lawyer, October 1992, 35]

Source: The Book of Skulls (1972), Chapter 7 (p. 25)

Six Principles of Political Realism, § 4.
Politics Among Nations (1948)
Context: Political realism is aware of the moral significance of political action. It is also aware of the ineluctable tension between the moral command and the requirements of successful political action. And it is unwilling to gloss over and obliterate that tension and thus to obfuscate both the moral and the political issue by making it appear as though the stark facts of politics were morally more satisfying than they actually are, and the moral law less exacting than it actually is.

Section 9 : Ethical Outlook
Founding Address (1876), Life and Destiny (1913)
Context: Theologians often say that faith must come first, and that morality must be deduced from faith. We say that morality must come first, and faith, to those whose nature fits them to entertain it, will come out of the experience of a deepened moral life as its richest, choicest fruit.
Precisely because moral culture is the aim, we cannot be content merely to lift the mass of mankind above the grosser forms of evil. We must try to advance the cause of humanity by developing in ourselves, as well as in others, a higher type of manhood and womanhood than the past has known.
To aid in the evolution of a new conscience, to inject living streams of moral force into the dry veins of materialistic communities is our aim.
We seek to come into touch with the ultimate power in things, the ultimate peace in things, which yet, in any literal sense, we know well that we cannot know. We seek to become morally certain — that is, certain for moral purposes — of what is beyond the reach of demonstration. But our moral optimism must include the darkest facts that pessimism can point to, include them and transcend them.