- Always and inevitably everyone underestimates the number of stupid individuals in circulation.
- The probability that a certain person will be stupid is independent of any other characteristic of that person.
- A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses.
- Non-stupid people always underestimate the damaging power of stupid individuals. In particular non-stupid people constantly forget that at all times and places and under any circumstances to deal and/or associate with stupid people always turns out to be a costly mistake.
- A stupid person is the most dangerous type of person.
It is almost impossible to identify oneself as a stupid person, because even people who are studiously and conscientiously non-stupid act in stupid ways (see #4) on occasion, usually without realizing the damage done. Therefore we are all, at times and potentially, stupid people.
Someone (I can't find the reference quickly) once said that "Everyone makes a few mistakes every day. The trick is to make them when nobody's looking, in trivial matters."
Addendum: The original rules were formulated under the belief that stupidity is a personal characteristic, inherent in certain individuals. I find this reductionistic and a poor match to the evidence, and I question the methods by which the original research was done. It makes more sense, given the laws of unintended consequences and the apparently consistent findings of stupidity across class, race and gender lines, to consider stupidity by its effects (which is in fact how the rules define it) rather than by its origins.
Just as it is possible for intelligent people to do stupid things, similarly dumb people (or institutions, or policies) may have unexpectedly good results for all concerned. Stupidity is contextual, not essential.