10 kinds of people

You can categorize people based on how they divide up everybody else. For example, psychologists classify people according to the Big Five personality traits, or other systems. Cops tend to divide people into cops, civilians, and scumbags.

Computer scientists divide people according to this:

There are 10 kinds of people. Those who understand binary notation, and those who do not.

In other words, those who get this joke and those who don't.

Some people divide according to religion, right-left politics, IQ, or some other litmus test.

Mathematician T. Tao brilliantly describes how he divides people:

One can broadly divide the outcomes of any given action into three categories: the worst-case scenario, the average-case scenario, and the best-case scenario. ... One can roughly subdivide different modes of thinking by what upper bounds and lower bounds one chooses to set: ...

Some of these distinctions might be incomprehensible to those who do not make them.

The previous post can be understood as Friedman advocating an advantage to one of Tao's types, altho Friedman doesn't suggest actually doing anything to separate those types.