It's very dangerous to believe people, I haven't for years.

Believing everyone is dangerous, but believing nobody is more dangerous.

I think it's important not to believe anyone when they tell you're good; maybe that's not healthy. But I think if you start to think of yourself the way that people you that you work with speak to you, then that's dangerous.

Not believing others implies that you yourself are deceitful. The liar suffers twice: he neither believes nor is believed.

Never believe all you hear or read about anyone.

You must never believe everything they say about a person. Generally speaking, most of it will be lies, half-truths at best.

I don’t want to believe them, I just don’t want to believe them

It is dangerous to be sincere unless you are also stupid.

It is no good my telling you. One never believes other people's experiences and one is only very gradually convinced by one's own.

No lesson seems to be so deeply inculcated by the experience of life as that you should never trust experts. If you believe doctors, nothing is wholesome: if you believe the theologians, nothing is innocent: if you believe the soldiers, nothing is safe. They all require their strong wine diluted by a very large admixture of insipid common sense.

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

Never believe anything that requires you to hate people who do not believe it.

I've tried to believe, but I don't, I can't, and there's no use pretending.

It is surely harmful to souls to make it a heresy to believe what is proved.