A lot of share-buying, not bargain-seeking, is designed to prop stock prices up. Thirty to 40 years ago, it was very profitable to look at companies that were aggressively buying their own shares. They were motivated simply to buy below what it was worth.

A banker who is allowed to borrow money at X and loan it out at X plus Y will just go crazy and do too much of it if the civilization doesn't have rules that prevent it.

The possibility that stock value in aggregate can become irrationally high is contrary to the hard-form "efficient market" theory that many of you once learned as gospel from your mistaken professors of yore. Your mistaken professors were too much influenced by "rational man" models of human behavior from economics and too little by "foolish man" models from psychology and real-world experience.

If you, like me, lived through 1973-74 or even the early 1990s... There was a waiting list to get OUT of the country club - that's when you know things are tough. If you live long enough, you'll see it.

The best armor of old age is a well-spent life preceding it.

Of course you want to drive that out of yourself because you want to be wise, not foolish. You also have to allow for the self-serving bias of everybody else because most people are not going to remove it all that successfully, the human condition being what it is. If you don't allow for self-serving bias in your conduct, again you're a fool.

You must know the big ideas in the big disciplines, and use them routinely - all of them, not just a few. Most people are trained in one model - economics, for example - and try to solve all problems in one way. You know the old saying: to the man with a hammer, the world looks like a nail. This is a dumb way of handling problems.