The stock market listing of SpaceX has led to an outpouring of celebration, from Wall Street to Silicon Valley. Yet those who rejoice in Elon Musk’s fortune surpassing the $1tn mark need to be reminded of a simple and vital truth: the mere existence of trillionaires is a major political and economic problem, probably the defining issue of our time.

Simply put, there is a fundamental tension between extreme wealth and the very possibility of democracy. Extreme wealth is always an extreme power. It’s the power to stifle competition, the power to shape public discourse, the power to influence policymaking, the power to buy elections, the power to stall social progress.

This problem is not new: all the thinkers of democracy, from Aristotle more than 2,000 years ago to Lea Ypi at the London School of Economics today, have highlighted the corrosive nature of extreme wealth for society.

Even conservative thinkers acknowledge it. James Madison, the father of the US constitution and a hero to today’s conservatives, famously wrote that wealth inequality is as poisonous for democracy as war. “In war, too, the discretionary power of the Executive is extended; its influence in dealing out offices, honors, and emoluments is multiplied … The same malignant aspect in republicanism may be traced in the inequality of fortunes,” he wrote

For some time, after the second world war, it looked like extreme wealth belonged to the past and that we could forget this problem. After the shocks of the wars and the rise of progressive income and inheritance taxation – with top marginal tax rates that reached nearly 100% in both the UK and the US in the postwar decades – extreme wealth had largely disappeared. But it’s now coming back in full force.

In 1989, the first........

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