Crossing the river by feeling each stone

Chris Blattman (HT Brad DeLong) has an excellent overview of the trial and error approach:

"I’d make a different point: the way I’ve learned how things operate is to work with a government or organization to try out a policy and succeed or fail. This kind of trial and error seems crucial to me. Karl Popper called this the piecemeal social engineer. Deng Xiaoping called it crossing the river by feeling each stone.

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This seems to be the way to overcome over-confidence and avoid the hubris that is associated with defending a defeated strategy.  This, of course, is the method of successful investment strategy:  try it out and be ready to change when it does not work.  Of course, ;-), you need to make sure that you do not sell at the low and buy at the top.