The only thing more dangerous than an idea is a belief. And by dangerous I don't mean thought-provoking. I mean: might get people killed.

Nothing is more dangerous than an idea when it is the only one you have.

Believing in an idea is dangerous! Because belief is absolute, and absolute, is unconditional, it is supreme, its ultimate and therefore fixed, which by definition will never be acceptable to change.'

There’s nothing more dangerous than a good idea.

Only ideals are dangerous.

"Dangerous" does not mean exciting or bold; it means likely to cause great harm. The most dangerous idea is the only dangerous idea: The idea that ideas can be dangerous.

The one thing that is more dangerous than true ignorance is the illusion of understanding.

An idea that is not dangerous is unworthy of being called an idea at all.” — Oscar Wilde, writer and poet

If there is anything more dangerous to the life of the mind than having no independent commitment to ideas, it is having an excess of commitment to some special and constricting idea.

No weapon is as dangerous as an idea. A weapon will kill you in that moment. A bad idea can kill you for a lifetime.

Once you've got — actually got — an idea that is whirring around so fast that no other light or contrary evidence can come in, I think it's very dangerous.

Ideas are dangerous, but the man to whom they are least dangerous is the man of ideas. He is acquainted with ideas, and moves among them like a lion-tamer. Ideas are dangerous, but the man to whom they are most dangerous is the man of no ideas. The man of no ideas will find the first idea fly to his head like wine to the head of a teetotaller. It is a common error, I think, among the Radical idealists of my own party and period to suggest that financiers and business men are a danger to the empire because they are so sordid or so materialistic. The truth is that financiers and business men are a danger to the empire because they can be sentimental about any sentiment, and idealistic about any ideal, any ideal that they find lying about, just as a boy who has not known much of women is apt too easily to take a woman for the woman, so these practical men, unaccustomed to causes, are always inclined to think that if a thing is proved to be an ideal it is proved to be the ideal.

Nothing is more dangerous than a dogmatic worldview - nothing more constraining, more blinding to innovation, more destructive of openness to novelty.

[A] theory is a very dangerous thing to have.