Self-will so ardent and active that it will break a world to pieces to make a stool to sit on.Richard Cecil
- It worked.
- His exclamation after the Trinity atomic bomb test, according to his brother in the documentary Day After Trinity
- I need physics more than friends.
- Letter to his brother
- It is with appreciation and gratefulness that I accept from you this scroll for the Los Alamos Laboratory, and for the men and women whose work and whose hearts have made it. It is our hope that in years to come we may look at the scroll and all that it signifies, with pride. Today that pride must be tempered by a profound concern. If atomic bombs are to be added as new weapons to the arsenals of a warring world, or to the arsenals of the nations preparing for war, then the time will come when mankind will curse the names of Los Alamos and Hiroshima. The people of this world must unite or they will perish. This war that has ravaged so much of the earth, has written these words. The atomic bomb has spelled them out for all men to understand. Other men have spoken them in other times, and of other wars, of other weapons. They have not prevailed. There are some misled by a false sense of human history, who hold that they will not prevail today. It is not for us to believe that. By our minds we are committed, committed to a world united, before the common peril, in law and in humanity.
- Acceptance Speech, Army-Navy "Excellence" Award, November 16, 1945
- Despite the vision and farseeing wisdom of our wartime heads of state, the physicists have felt the peculiarly intimate responsibility for suggesting, for supporting, and in the end, in large measure, for achieving the realization of atomic weapons. Nor can we forget that these weapons as they were in fact used dramatized so mercilessly the inhumanity and evil of modern war.In some sort of crude sense which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose.
- Physics in the Contemporary World, Arthur D. Little Memorial Lecture at M.I.T. (November 25, 1947)
- There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. Our political life is also predicated on openness. We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress.
- Barnett L., "J. Robert Oppenheimer," Life, Vol. 7, No. 9, International Edition, October 24, 1949, pp.52-59, p.58) 
- Sometimes a partial version (the final sentence) is misattributed to Marcel Proust.
- The open society, the unrestricted access to knowledge, the unplanned and uninhibited association of men for its furtherance - these are what may make a vast, complex, ever growing, ever changing, ever more specialized and expert technological world, nevertheless a world of human community.
- Science and the Common Understanding (1953)
- It's not that I don't feel bad about it. It's just that I don't feel worse today than what I felt yesterday.
- Response to question on his feelings about the atomic bombings, while visiting Japan in 1960.
- We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Krishna is trying to persuade Arjun that he should do his duty and to impress him takes on his multi-armed form and says, "Now I am become Death, the destroyer of worlds." I suppose we all thought that, one way or another.
- Interview about the Trinity explosion, first broadcast as part of the television documentary The Decision to Drop the Bomb, produced by Fred Freed, NBC White Paper, 1965; Oppenheimer is quoting a line from the Bhagavad Gita spoken by Krishna, who is revered in Hindu traditions as one of the major incarnations of Vishnu.
- Many experts believe that the Baghavad-Gita passage should be translated "I am become Time, the destroyer of worlds."
- When you see something that is technically sweet, you go ahead and do it and argue about what to do about it only after you've had your technical success. That is the way it was with the atomic bomb.
- Testifying in his defense in his 1954 security hearings (page 81 of the official transcript)
- It is perfectly obvious that the whole world is going to hell. The only possible chance that it might not is that we do not attempt to prevent it from doing so.
- As quoted in Play to Live (1982) by Alan Watts
- Everyone wants rather to be pleasing to women and that desire is not altogether, though it is very largely, a manifestation of vanity. But one cannot aim to be pleasing to women any more than one can aim to have taste, or beauty of expression, or happiness; for these things are not specific aims which one may learn to attain; they are descriptions of the adequacy of one's living. To try to be happy is to try to build a machine with no other specification than that it shall run noiselessly.
- Letter to his brother, Frank 1929
- The general notions about human understanding… which are illustrated by discoveries in atomic physics are not in the nature of things wholly unfamiliar, wholly unheard of or new. Even in our own culture they have a history, and in Buddhist and Hindu thought a more considerable and central place. What we shall find [in modern physics] is an exemplification, an encouragement, and a refinement of old wisdom.
- The juxtaposition of Western civilization's most terrifying scientific achievement with the most dazzling description of the mystical experience given to us by the Bhagavad Gita, India's greatest literary monument.
- Truth, not a pet, is man's best friend.
- The Optimist thinks this is the best of all possible worlds, the Pessimist fears it is true.
- This is derived from a statement of James Branch Cabell, in The Silver Stallion (1926) : The optimist proclaims that we live in the best of all possible worlds; and the pessimist fears this is true.
- Genius sees the answer before the question.
- The fictional (and hallucinatory) character "William Parcher" in A Beautiful Mind quotes Oppenheimer as saying this. There are no published sources indicating Oppenheimer actually did so.
- Biography and online exhibit created for the centennial of his birth
- Biographical Memoirs: Robert Oppenheimer by Hans Bethe
- On Atomic Energy, Problems to CivilizationTalk at UC Berkeley, Nov. 6, 1946 (online audio file)
- Decision and Opinions of the US AEC in the Matter of Dr. J. Robert Oppenheimer
- Was Oppenheimer a member of the Communist Party?, notes and documents on the question (still in historical debate) by the historian Gregg Herken