First Law

We always underestimate the number of stupid people.
People we had thought to be rational and intelligent suddenly turn out to be unquestionably stupid.
Day after day we are hampered in whatever we do by stupid people who invariably turn up in the least appropriate place.
It is impossible to set a percentage, because any number we choose will be too small.

Second Law

Third ('Golden') Law

A stupid person is someone who causes damage to another person, or a group of people, without any advantage accruing to himself (or herself) -- or even with some resultant self-damage.

Fourth Law

Non-stupid people always underestimate the damaging power of stupid people. They constantly forget that at any moment, and in any circumstance, associating with stupid people invariably constitutes an expensive mistake.

Fifth Law

A stupid person is the most dangerous person in existence. This is probably the most widely understood of the Laws, if only because it is common knowledge that intelligent people, hostile as they might be, are predictable, while stupid people are not. When stupidity gets into the act, the damage is enormously greater than the benefit to anyone:
The single most dangerous factor in any human society is stupidity.

A stupid person is more dangerous than a bandit.

When stupidity gets into the act, the damage is enormously greater than the benefit to anyone.

Stupid people don't know they are stupid, and that is one more reason why they are extremely dangerous.

(This summary was prepared by me, and is posted with the author's approval.)