In the spring of 1720, a London coffeehouse called Jonathan's buzzed with a new kind of madness. Men who had never owned a share of anything were mortgaging their homes to buy stock in the South Sea Company — a firm whose actual business was so vague that its own directors couldn't explain it.

The company had one genuine asset: a government-granted monopoly on trade with South America. But the trade itself was almost nonexistent. What the South Sea Company really sold was a story — a narrative of limitless wealth just over the horizon, backed by complicated financial instruments that nobody quite understood.

The Madness of Sir Isaac

Even Isaac Newton, the most rational mind in England, couldn't resist. In early 1720, he invested a modest sum and made a tidy profit. He sold his shares in April, reportedly telling a friend, "I can calculate the motions of the heavenly bodies, but not the madness of people."

Then he watched the stock keep climbing. By June, Newton bought back in — at three times his original price. He invested his life savings.

The stock peaked at £1,050 in late June. By September, it had crashed to under £200. Newton lost £20,000 — roughly $5 million in today's money. He refused to hear the words "South Sea" spoken in his presence for the rest of his life.

The Machine Behind the Mania

What made the bubble so devastating wasn't just greed. It was a sophisticated feedback loop that the company deliberately engineered. South Sea directors lent money to investors to buy South Sea stock, which pushed the price up, which made the stock look like good collateral, which justified more lending.

The directors themselves were selling into the rally. They knew the scheme was hollow. Parliament had been bribed — dozens of MPs held shares given to them for free, ensuring no awkward questions about the company's actual revenues (which were nearly zero).

When the bubble burst, the fallout was swift and merciless. The Chancellor of the Exchequer was sent to the Tower of London. The Postmaster General took poison and died. Thousands of families were ruined overnight.

The Echo

Now, three centuries later, the pattern is unmistakable.

Today's headlines tell a strikingly similar story. The AI investment frenzy has pushed company valuations into territory that even optimists struggle to justify. Companies with minimal revenue are commanding market caps in the billions, fueled by narratives of limitless future potential.

The structural parallels run deeper than simple speculation. Like the South Sea Company, today's AI darlings benefit from a feedback loop: venture capital flows in, valuations rise, rising valuations attract more capital. Insiders sell into the rally while retail investors pile in.

The South Sea Bubble didn't end capitalism. It didn't even end speculation. But it did trigger Britain's first major financial regulations — the Bubble Act of 1720 — and it destroyed the savings of a generation that believed a good story was the same thing as a good investment.

Newton's epitaph for the affair was characteristically precise: he could calculate the motion of heavenly bodies but not the madness of people.

Three hundred years later, we've upgraded the heavenly bodies to neural networks. The madness, it seems, needs no upgrade at all.