The interesting thing is the field is so big - it's enormous. One thing a modern civilization needs is energy.

The idea of excessive diversification is madness. Wide diversification, which necessarily includes investment in mediocre businesses, only guarantees ordinary results.

For society, the Internet is wonderful, but for capitalists, it will be a net negative. It will increase efficiency, but lots of things increase efficiency without increasing profits. It is way more likely to make American businesses less profitable than more profitable. This is perfectly obvious, but very little understood.

A lot of people with high IQs are terrible investors because they've got terrible temperaments. And that is why we say that having a certain kind of temperament is more important than brains. You need to keep raw irrational emotion under control. You need patience and discipline and an ability to take losses and adversity without going crazy. You need an ability to not be driven crazy by extreme success

We're guessing at our future opportunity cost. Warrenis guessing that he'll have the opportunity to put capital out at high rates of return, so he's not willing to put it out at less than 10% now. But if we knew interest rates would stay at 1%, we'd change. Our hurdles reflect our estimate of future opportunity costs.

Darwin paid particular attention to disconfirming evidence. Objectivity maintenance routines are totally required in life if you're going to be a great thinker.

Berkshireis in the business of making easy predictions If a deal looks too hard, the partners simply shelve it.