Julius Caesar's IQ: What His Books, Battles and Calendar Show

Why Caesar Has No Scholarly IQ

IQ testing began in 1905, nearly two millennia after Caesar's assassination. The only rigorous way to estimate a historical IQ is Catharine Cox's method, published by Stanford University Press in 1926: rate the documented achievements of childhood and youth against age norms. Cox restricted her sample to people born between 1450 and 1850, where such records survive. Caesar's childhood left almost none.

The "150+" number that appears online comes from an IQ-test marketing site. The site itself concedes no test report exists and describes the figure as its own comparison estimate. That is not evidence. For his full life, see our Julius Caesar profile; for the limits of the method, read historical IQ estimates explained.

The Writer: Seven Books in Plain Latin

Caesar is the rare conqueror who wrote his own history, and wrote it well. He composed books 1 through 7 of the Commentarii de Bello Gallico, covering his campaigns from 58 BC; his officer Aulus Hirtius added book 8 after Caesar's death. The narrative runs in the third person, with Caesar as a character in his own account.

Cicero, Rome's greatest orator and no friend of Caesar's politics, reviewed the commentaries by 46 BC and praised their bare, direct style, in Suetonius's rendering "stripped of all rhetorical adornment." Two thousand years later, the Gallic War remains the first authentic text traditionally assigned to students of Latin.

He also wrote about language itself. Suetonius records a two-book treatise, On Analogy, on correct Latin usage, composed while crossing the Alps on the way back to his army. He wrote two books attacking Cato and a poem, Iter, on a trip to Spain. The grammar treatise is lost.

Four Letters at Once

Ancient writers describe a mind that ran several tracks at once. Pliny the Elder, writing more than a century later, reports that Caesar would write or read while dictating and listening at the same time, and that he dictated four important letters at once to his secretaries, or seven when he had nothing else to do.

Suetonius adds that Caesar covered a hundred miles a day in a hired carriage and wrote confidential letters in cipher, replacing each letter with the one three places later in the alphabet: D for A. That simple shift still carries his name as the Caesar cipher.

These are anecdotes, not measurements, and Roman biographers liked a good story. They are consistent, however, with a documented output of campaigns, speeches, books and legislation that few individuals in any era have matched.

Alesia: Engineering as Strategy

In September 52 BC, Caesar trapped the Gallic leader Vercingetorix inside the hill town of Alesia. He then built two rings of fortifications: an inner line of 11 Roman miles, about 16 kilometers, with 23 redoubts, to hold the town, and an outer line of 14 Roman miles, about 20.7 kilometers, to hold off a relief army.

His force numbered perhaps 30,000 to 50,000 legionaries plus auxiliaries. Modern estimates put the Gallic relief army at 50,000 to 100,000. Caesar held both fronts. Vercingetorix surrendered, and Gallic independence in what is now France and Belgium ended. The siege was a problem in logistics and geometry as much as in combat.

A Calendar That Outlived Rome

Rome's old calendar had drifted badly from the seasons. In 46 BC Caesar replaced it. Working with the astronomer Sosigenes of Alexandria, whom Pliny names as his adviser, he set a year of 365 days with an extra day every fourth year, an average of 365.25 days.

To realign the calendar, he stretched 46 BC to 445 days by inserting two extra months. The new system took effect on 1 January 45 BC. It remained the dominant calendar of the Western world for more than 1,600 years, until Pope Gregory XIII revised it in 1582, and parts of the Eastern Orthodox Church still use it. Few political acts have lasted longer.

Caesar Against Alexander and Napoleon

Neither Caesar nor Alexander the Great nor Hannibal has a scholarly IQ estimate. Among great commanders, the research-based numbers begin with those born after 1450. Napoleon is the benchmark: Cox estimated 135 for his childhood and 140 for early adulthood, a level explained on our IQ 140 page.

Caesar has one distinction the others lack: a large, surviving body of his own prose. Compare the careers on Alexander vs. Caesar and Napoleon vs. Caesar, and see the full table in military leaders ranked by IQ.

Ambition Is Not on the Test

Caesar crossed the Rubicon in January 49 BC and started a civil war. By 44 BC he was dictator for life. On 15 March of that year, senators stabbed him to death in the Theatre of Pompey. Intelligence did not protect him from misjudging the men around him.

Pliny also recorded the cost of the career: 1,192,000 people killed in Caesar's battles, a total Pliny refused to count as glory. An IQ score measures reasoning. It says nothing about ambition, ruthlessness or the judgment that failed on the Ides of March.

How We Assessed This

We found no scholarly IQ estimate for Caesar and report none. Claims about his working habits come from Pliny the Elder and Suetonius, both writing long after his death; we label them as ancient reports. Dates and figures follow standard modern references.

Editorial standard: IQ figures for historical figures are retrospective estimates and are labeled as such; scores for living people appear only when the person disclosed them or a reputable outlet reported them. Corrections: contact the editors.