The highest IQ philosophers in history

Cox's 1926 study is the source of most famous philosopher IQs. She rated people born between 1450 and 1850 from what they could do at each age, and philosophers often had extraordinary documented childhoods: John Stuart Mill learning Greek at three, Leibniz teaching himself Latin at eight, Grotius entering university at eleven. Those records push Cox's figures towards the top of her scale.

For thinkers outside her window, such as Plato and Aristotle before it or Popper and Arendt after it, the numbers are editorial markers based on the documented work. They carry very low confidence and are labelled that way. The list also includes theologians, political theorists and essayists whose main contribution was ideas.

Systematic philosophers rank high: Kant, Hume, Aquinas and Spinoza built complete systems with long chains of argument, the kind of reasoning that most resembles what intelligence tests sample. Essayists and moralists such as Montaigne and Seneca sit a little lower, not because their thought is less valuable but because their gifts were judgement and style rather than formal construction.

Several of the highest figures belong to people better known for other things. Hugo Grotius, at 200 in Cox's corrected estimate, was a jurist; George Berkeley, at 190, was a bishop who also exposed a real flaw in Newton's calculus. Cox's ratings measured precocity across every field, so a philosopher's rank reflects the whole life record, not only the philosophy.

Disagreement among philosophers is not disagreement in IQ. Schopenhauer despised Hegel, Popper clashed with Wittgenstein and Camus broke with Sartre. The table can tell you roughly how each was rated; it cannot tell you who was right.

Cox's numbers are ratio-style estimates on an old scale that runs high, so LifeScore profiles bring them down, usually by 20 to 30 points, and show both numbers. Goethe's 210 becomes a working estimate of 190, and Berkeley's 190 a working estimate of 165. The range on each profile covers both.