But there is a second lesson in Graham’s approach. The only thing
you can be confident of while forecasting future stock returns is that
you will probably turn out to be wrong. The only indisputable truth that
the past teaches us is that the future will always surprise us—always!
And the corollary to that law of financial history is that the markets will
most brutally surprise the very people who are most certain that their
views about the future are right. Staying humble about your forecast-
ing powers, as Graham did, will keep you from risking too much on a
view of the future that may well turn out to be wrong.
possunt quia posse videntur