“Conscience is, in most men, an anticipation of the opinions of others.”

Napoleon : In His Own Words (1916)
Context: Conscience is the most sacred thing among men. Every man has within him a still small voice, which tells him that nothing on earth can oblige him to believe that which he does not believe. The worst of all tyrannies is that which obliges eighteen-twentieths of a nation to embrace a religion contrary to their beliefs, under penalty of being denied their rights as citizens and of owning property, which, in effect, is the same thing as being without a country.

As quoted in Isms (2006) by Gregory Bergman, p. 105
Attributed

Speech to the Electors of Bristol (3 November 1774); reported in The Works of the Right Honorable Edmund Burke (1899), vol. 2, p. 95
Context: Certainly, Gentlemen, it ought to be the happiness and glory of a representative to live in the strictest union, the closest correspondence, and the most unreserved communication with his constituents. Their wishes ought to have great weight with him; their opinions high respect; their business unremitted attention. It is his duty to sacrifice his repose, his pleasure, his satisfactions, to theirs,—and above all, ever, and in all cases, to prefer their interest to his own.
But his unbiased opinion, his mature judgment, his enlightened conscience, he ought not to sacrifice to you, to any man, or to any set of men living. These he does not derive from your pleasure,—no, nor from the law and the Constitution. They are a trust from Providence, for the abuse of which he is deeply answerable. Your representative owes you, not his industry only, but his judgment; and he betrays instead of serving you if he sacrifices it to your opinion.

Stanza 27.
Beppo (1818)

Inaugural Address Delivered to the University of St. Andrews, Feb. 1st 1867 (1867) p. 36. http://books.google.com/books?id=DFNAAAAAcAAJ&pg=PA36
Source: Inaugural Address Delivered to the University of St Andrews, 2/1/1867
Context: What is called the Law of Nations is not properly law, but a part of ethics: a set of moral rules, accepted as authoritative by civilized states. It is true that these rules neither are nor ought to be of eternal obligation, but do and must vary more or less from age to age, as the consciences of nations become more enlightened, and the exigences of political society undergo change. But the rules mostly were at their origin, and still are, an application of the maxims of honesty and humanity to the intercourse of states. They were introduced by the moral sentiments of mankind, or by their sense of the general interest, to mitigate the crimes and sufferings of a state of war, and to restrain governments and nations from unjust or dishonest conduct towards one another in time of peace. Since every country stands in numerous and various relations with the other countries of the world, and many, our own among the number, exercise actual authority over some of these, a knowledge of the established rules of international morality is essential to the duty of every nation, and therefore of every person in it who helps to make up the nation, and whose voice and feeling form a part of what is called public opinion. Let not any one pacify his conscience by the delusion that he can do no harm if he takes no part, and forms no opinion. Bad men need nothing more to compass their ends, than that good men should look on and do nothing. He is not a good man who, without a protest, allows wrong to be committed in his name, and with the means which he helps to supply, because he will not trouble himself to use his mind on the subject. It depends on the habit of attending to and looking into public transactions, and on the degree of information and solid judgment respecting them that exists in the community, whether the conduct of the nation as a nation, both within itself and towards others, shall be selfish, corrupt, and tyrannical, or rational and enlightened, just and noble.

Nobel Peace Prize Speech (1975)

Source: A Room of One's Own (1929), Ch. 3, p. 58

Book XXII, sec. 38
History of Rome