A reader recently asked me to estimate the IQ of Bertrand Russell.  This reader is probably extremely smart: The fact that he’s interested in IQ at all is one sign of intelligence, but the fact that he inquired about Bertrand Russell (as opposed to some pop culture celeb or politician) is another sign.

The two most salient facts about Bertrand Russell is that he was an incredibly eminent intellectual; journalist Daniel Seligman described him as arguably the most intelligent man of the 20th century, and yet he couldn’t lean to make a cup of tea, despite his wife leaving him detailed instructions.  He also couldn’t make his hearing aid work.

To get a sense of Russell’s IQ, we begin by noting that roughly the year Russell won his Nobel prize, the average IQ of the 64 eminent scientists in the Roe study was about 155.  The dumbest of these eminent scientists had an IQ around 120, 35 points below the mean of the whole group.  But I bet even he or she could learn to make tea.

In low complexity jobs (i.e. making tea in a restaurant), the correlation between IQ and job performance is about 0.23.  So even though Russell was likely dumber than all of Roe’s elite scientists at learning to  make tea, his actual IQ was probably only 23% as low as the dumbest Roe scientist.

So since the dumbest Roe scientist was 35 points dumber than the average elite scientist of that time, Russell was probably 0.23(35) = 8 points dumber than the average Roe scientist.

If the average Roe scientist had an IQ of 155, Russell likely had an IQ of 155 – 8 = 147.

An IQ of 147 implies that only one in a thousand whites of Russell’s era were as smart or smarter than him.