Social arithmetic is a way of checking generalisations about nations, genders, social classes, age-groups etc. It does this by estimating the number or proportion of people they apply to. e.g. applied to the cliché that 'War is inevitable because humans are innately violent' cuts the generalisation in half by excluding women, and then cuts it further by considering how many men in a sample of 100 are actually the warmakers, in different cultures and at different periods of history.

'Men are all rapists' is tested by how many men in a sample of 100 would ever be violent sexually, and of those who are, how often and under what circumstances, in different times and places of history.

Similarly with the generalisation, that 'women are liable to be silly, and many men are liable to be stupid'.

This theory is in some ways a democratic argument - because it says that what individuals do does matter. They are not helpless.

When anyone deliberately collects biros, or regards the firm's property as perks, or enjoys evading tax, or hits their girlfriends, they are helping to push 'average behaviour' into a criminal mode, which fosters increased numbers of deliberately antisocial individuals at the lower extreme, and makes it harder for others to be honest. Road speeds are a clear example of how this can happen. When enough drivers are doing 80 on a suburban road marked at 60, then the irresponsible drivers will go at 100 kph, and the more law-abiding drivers feel forced to go at 80 kph too, regardless of personal wishes or feeling that they are not very safe drivers at that speed.