The South Sea Bubble

"I can calculate the motion of heavenly bodies, but not the madness of people." Newton probably never said it — and we don't actually know what he lost. What the records really show.

The story everyone knows

It comes, for most readers, from Benjamin Graham’s The Intelligent Investor: Newton bought South Sea stock early, sold at a £7,000 profit, watched it keep rising, bought back in near the top — and lost £20,000 when the bubble burst in 1720. And afterward, supposedly, he remarked that he could calculate the motion of heavenly bodies but not the madness of people.

It is a wonderful story. Almost none of it is documented.

What the records show

Recent research — notably Andrew Odlyzko’s forensic work on Newton’s surviving financial papers, and the University of Oxford’s “Newton and the Mint” project — has reconstructed what can actually be proved:

• Newton was a substantial and long-term investor in South Sea stock, holding significant amounts (around £13,000–£22,000 in various forms) through the bubble years.
• He did sell some holdings in 1720 and did buy back in — the pattern of selling early and re-entering is consistent with the records.
• But the £20,000 loss figure is an estimate, not a documented total, and the reconstruction shows Newton may have done less badly than legend says: much of his wealth was in government securities that were converted, not annihilated.
• The Oxford project’s verdict: it is likely that Newton lost some money, but the evidence is inconclusive — and the confident numbers in the popular story outrun the documents.

The quote he never said

“I can calculate the motion of heavenly bodies, but not the madness of people” has no contemporary source. It appears nowhere in Newton’s writings or in any account written by someone who knew him. It belongs on the Sayings page’s never-said list — a Victorian-era attribution that flatters our image of the sage undone by the crowd.

The Mint’s part in the story

Irony upon irony: after the crash, it was Newton’s own institution — the Mint — that was called on to handle the bail-out, producing large quantities of silver coin for the Bank of England’s emergency operations. The Master of the Mint who had ridden one bubble was now mopping up after it.

Source notes

• The popular account: B. Graham, The Intelligent Investor (1949 and later eds.).
• Forensic reconstruction: A. Odlyzko, “Isaac Newton and the perils of the financial South Sea” (research paper, University of Minnesota).
• Oxford “Newton and the Mint” project: concludes evidence of loss is likely but inconclusive; specific figures should be treated as estimates.
• The “madness of people” remark: no contemporary source; listed here as misattributed.
• Mint’s post-crash role: documented in the Oxford project materials.