I feel strongly about not criticizing entrepreneurs. It’s hard enough to start a company without the peanut gallery razzing you. And really, what good are you doing by being critical? Companies that are going to fail are going to fail without you wishing it on them, while your criticism might hurt companies that are on the path to success. What is constructive about your criticism?

The rationalization I always hear, from people who I suspect simply enjoy blood-sport, is: “how can we learn unless we look at what people are doing wrong?”

The easy answer is that there’s a difference between a good post-mortem and criticizing something while people are trying to make a go of it. And there’s a difference between a good post-mortem and 20/20 hindsight. The only person who can credibly make that distinction is the founder. Anyone else would have the unavoidable whiff of smugness.

There’s a better answer and I think this is important. It’s that criticism of failed companies is never very useful. Never.

You don’t learn from failure. You can’t learn anything from failure.

Ok, Neumann, you say. I have learned from failure. That time I burned my toast I learned to set the toaster lower. Now I don’t burn my toast. Ha.

When I was a kid I wrote a computer program that learned to win at tic-tac-toe. First it build a decision tree of every possible tic-tac-toe game. Then it played you. Every time it lost it pruned that branch of the tree until only the wins or draws were left. It learned from failure.

Try that with checkers. Harder.

Try that with chess. Hard to impossible.

Try it with starting a company.

Any complicated system is too complicated to learn from failure. Yes, you can learn a few tricks, like: “don’t spend all your money on fancy chairs” or “don’t hire your college drinking buddies as EVPs of Business Development.” But you can also spend your life learning about every mistake every startup founder ever made in all of recorded history and I guarantee that when you start your company you will discover all new mistakes to make. That is how life is.

All you can learn from failure is to avoid that particular kind of failure. And so what? There are too many other kinds of failure for that to make any difference. You need to learn from success. You should be spending your time trying to learn from success.

The successful entrepreneurs I have known have had the ability to look at a failure, any failure, and pull out the couple of things that were done right. These are what they focused on. Think about the successful entrepreneurs you know or have read about. This is just true.

If you’re going to learn from failure you need to learn how to avoid every possible way you can fail. It’s a waste of your time. You only need to learn one way to succeed.