Richard Feynman on knowing something

In the video The Pleasure of Finding Things Out I love this profound quote by Richard Feynman. He's talking about pseudo-science, but it has broad applicability:

But I have an the advantage of having found out how hard it is to really get to know something. How careful you have to be about checking your experiments. How easy it is to make mistakes and fool yourself.

I know what it means to know something, and therefore I see how they get their information, and I can't believe they claim to know something. They haven't done the work necessary. They haven't done the checks necessary. They have done the care necessary.

I think about this quote, when I see people making simple-minded, black-and-white statements on subjects like politics, economics, health and religion.