If you have competence, you pretty much know its boundaries already. To ask the question (of whether you are past the boundary) is to answer it.

Another thing I think should be avoided is extremely intense ideology because it cabbages up one's mind. You see it a lot with T.V. preachers (many have minds made of cabbage) but it can also happen with political ideology. When you're young it's easy to drift into loyalties and when you announce that you're a loyal member and you start shouting the orthodox ideology out, what you're doing is pounding it in, pounding it in, and you're gradually ruining your mind. So you want to be very, very careful of this ideology. It's a big danger.

If you get into the mental habit of relating what you're reading to the basic structure of the underlying ideas being demonstrated, you gradually accumulate some wisdom.

Wrigley is a great business, but that doesn't solve the problem. Buying great businesses at advantageous prices is very tough.

Sears had layers and layers of people it didn't need. It was very bureaucratic. It was slow to think. And there was an established way of thinking. If you poked your head up with a new thought, the system kind of turned against you. It was everything in the way of a dysfunctional big bureaucracy that you would expect.

Once you get into debt, it’s hell to get out. Don’t let credit card debt carry over. You can’t get ahead paying eighteen percent.

I'm not entitled to have an opinion unless I can state the arguments against my position better than the people who are in opposition. I think that I am qualified to speak only when I've reached that state.