“Some good must come by clinging to the right. Conscience is a man's compass, and though the needle sometimes deviates, though one often perceives irregularities in directing one's course by it, still one must try to follow its direction.”

The Echo.

Nagara Sutta, Samyutta Nikaya II.124, translated by Thanissaro Bhikkhu
Pali Canon, Sutta Pitaka, Samyutta Nikaya (Connected Discourses)

Whig Circular (1843), reported in Richard Watson Gilder and Daniel Fish Complete Works of Abraham Lincoln, Volume 1 (1905)
1840s

Source: Percy Jackson's Greek Gods

Source: The 20th century capitalist revolution. 1954, p. 113-114; as cited in Prashker (1954)

That's what It Is
Albums, The 3rd World (2008)

Dijkstra (1972) The Humble Programmer http://www.cs.utexas.edu/users/EWD/transcriptions/EWD03xx/EWD340.html (EWD340).
1970s
Context: After having programmed for some three years, I had a discussion with A. van Wijngaarden, who was then my boss at the Mathematical Center in Amsterdam, a discussion for which I shall remain grateful to him as long as I live. The point was that I was supposed to study theoretical physics at the University of Leiden simultaneously, and as I found the two activities harder and harder to combine, I had to make up my mind, either to stop programming and become a real, respectable theoretical physicist, or to carry my study of physics to a formal completion only, with a minimum of effort, and to become....., yes what? A programmer? But was that a respectable profession? For after all, what was programming? Where was the sound body of knowledge that could support it as an intellectually respectable discipline? I remember quite vividly how I envied my hardware colleagues, who, when asked about their professional competence, could at least point out that they knew everything about vacuum tubes, amplifiers and the rest, whereas I felt that, when faced with that question, I would stand empty-handed. Full of misgivings I knocked on van Wijngaarden’s office door, asking him whether I could “speak to him for a moment”; when I left his office a number of hours later, I was another person. For after having listened to my problems patiently, he agreed that up till that moment there was not much of a programming discipline, but then he went on to explain quietly that automatic computers were here to stay, that we were just at the beginning and could not I be one of the persons called to make programming a respectable discipline in the years to come? This was a turning point in my life and I completed my study of physics formally as quickly as I could. One moral of the above story is, of course, that we must be very careful when we give advice to younger people; sometimes they follow it!

What then must we do? (1886)
Context: This new fraud is just like the old ones: its essence lies in substituting something external for the use of our own reason and conscience and that of our predecessors: in the Church teaching this external thing was revelation, in the scientific teaching it is observation. The trick played by this science is to destroy man's faith in reason and conscience by directing attention to the grossest deviations from the use of human reason and conscience, and having clothed the deception in a scientific theory, to assure them that by acquiring knowledge of external phenomena they will get to know indubitable facts which will reveal to them the law of man's life. And the mental demoralization consists in this, that coming to believe that things which should be decided by conscience and reason are decided by observation, these people lose their consciousness of good and evil and become incapable of understanding the expression and definitions of good and evil that have been formed by the whole preceding life of humanity. All this, in their jargon, is conditional and subjective. It must all be abandoned - they say - the truth cannot be understood by one's reason, for one may err, but there is another path which is infallible and almost mechanical: one must study facts. And facts must be studied on the basis of the scientists' science, that is, on the basis of two unfounded propositions: positivism and evolution which are put forward as indubitable truths. And the reigning science, with not less misleading solemnity than the Church, announces that the solution of all questions of life is only possible by the study of the facts of nature, and especially of organisms. A frivolous crowd of youths mastered by the novelty of this authority, which is as yet not merely not destroyed but not even touched by criticism, throws itself into the study of these facts of natural science as the sole path which, according to the assertions of the prevailing doctrine, can lead to the elucidation of the questions of life. But the further these disciples advance in this study the further and further are they removed not only from the possibility but even from the very thought of solving life's problems, and the more they become accustomed not so much to observe as to take on trust what they are told of the observations of others (to believe in cells, in protoplasm, in the fourth state of matter,1 &c.), the more and more does the form hide the contents from them; the more and more do they lose consciousness of good and evil and capacity to understand the expressions and definitions of good and evil worked out by the whole preceding life of humanity; the more and more do they adopt the specialized scientific jargon of conventional expressions which have no general human significance; the farther and farther do they wander among the debris of quite unilluminated observations; the more and more do they lose capacity not only to think independently but even to under-stand another man's fresh human thought lying outside their Talmud; and, what is most important, they pass their best years in growing unaccustomed to life, that is, to labour, and grow accustomed to consider their condition justified, while they become physically good-for-nothing parasites. And just like the theologians and the Talmudists they completely castrate their brains and become eunuchs of thought. And just like them, to the degree to which they become stupefied, they acquire a self-confidence which deprives them for ever of the possibility of returning to a simple clear and human way of thinking.

"Remaining Awake Through a Great Revolution" (31 March 1968)
1960s
Variant: There comes a time when one must take a position that is neither safe, nor politic, nor popular, but he must take it because conscience tells him it is right.
Source: A Testament of Hope: The Essential Writings and Speeches
Context: On some positions, Cowardice asks the question, "Is it safe?" Expediency asks the question, "Is it politic?" And Vanity comes along and asks the question, "Is it popular?" But Conscience asks the question "Is it right?" And there comes a time when one must take a position that is neither safe, nor politic, nor popular, but he must do it because Conscience tells him it is right.
Context: On some positions, Cowardice asks the question, "Is it safe?" Expediency asks the question, "Is it politic?" And Vanity comes along and asks the question, "Is it popular?" But Conscience asks the question "Is it right?" And there comes a time when one must take a position that is neither safe, nor politic, nor popular, but he must do it because Conscience tells him it is right. I believe today that there is a need for all people of good will to come together with a massive act of conscience and say in the words of the old Negro spiritual, "We ain't goin' study war no more." This is the challenge facing modern man.