Understanding how to be a good investor makes you a better business manager and vice versa.

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

A great business at a fair price is superior to a fair business at a great price.

I don't have the slightest interest in gold. I like understanding what works and what doesn't in human systems. To me that's not optional; that's a moral obligation. If you're capable of understanding the world, you have a moral obligation to become rational. And I don't see how you become rational hoarding gold. Even if it works, you're a jerk.

In fact I've probably never seen such a wide moat.

Part of that, I think, is being able to tune out folly, as distinguished from recognizing wisdom. You've got whole categories of things you just bat away so your brain isn't cluttered with them. That way, you're better able to pick up a few sensible things to do.

Derivative trading with mark-to-market accounting degenerates into mark-to-model. Two firms make a big derivative trade and the accountants on both sides show a large profit from the same trade.