I come not to mock Ben Carson for forgetting that Thomas Jefferson was in France when the Constitution and Bill of Rights were drafted, but to thank him for (unwittingly) raising the topic. My thesis is this: We should be thankful Jefferson was away. Notwithstanding the genius of the Declaration of Independence, its principal draftsman had truly terrible views about what a constitution should be like. If we’d followed them, we wouldn’t have the Constitution we revere. In fact, I don’t think we’d have much of a constitution at all.

You don’t have to take my word for it. Jefferson explained his chief constitutional ideas to James Madison, who was in fact the inventor of the Constitution, in a letter he originally wrote in September 1789 while in Paris, and then sent in January 1790, when he returned home. Madison was horrified, and rightly.

Jefferson’s letter started with an intriguing claim: that the earth belongs to the living only “in usufruct,” which meant as a kind of trust for future generations. With the pseudo- certainty of the scientifically minded Enlightenment philosopher he was, Jefferson set the period of a generation as exactly 19 (!) years. He argued “that neither the legislature, nor the nation itself, can validly contract more debt than they may pay within their own age, or within the term of 19 years” — the length of a generation.

To the extent this was a moral argument against a national debt too big to be retired, it was certainly creative, and perhaps even plausible. But Jefferson wasn’t done. He went on to insist that “on similar ground it may be proved that no society can make a perpetual constitution, or even a perpetual law. The earth belongs always the living generation.”

This logic brought him to a startling view: “Every constitution then, and every law, naturally expires at the end of 19 years. If it be enforced longer, it is an act of force, and not of right.”

Jefferson was making an assertion of truly astonishing proportion: that every constitution and every law must sunset after 19 years, or else was invalid as a matter of natural law. The argument included the hallmarks of the Declaration of Independence. It depended on what Jefferson considered a self- evident matter of natural right. And argument was in short supply compared to bold assertion.

When Madison got the letter, he knew he’d have to respond. After politely telling Jefferson that his “great idea” would be useful to the legislature considering how much debt to take on, he set out to refute Jefferson point by point.

Philosophically, Madison told Jefferson that he was confused about natural rights. If the earth was “the gift of nature to the living,” then that meant at most that natural things, like the earth, must be handed down intact. But humans often made improvements that benefited future generations — and those improvements required investment. The American Revolution had been funded by debt to benefit American posterity. Future generations could certainly be obligated to pay back debts incurred for their own benefit.

Madison saved his strongest criticism for the extreme impracticality of Jefferson’s idea. A constitution that dissolved every 19 years would create an “interregnum” before new constitution could be drafted during which property rights would be totally uncertain.

The impending fight over property rights would lead to “violent struggles” between property holders who wanted to keep the status quo and revolutionaries who wanted to change it. The result would be “anarchy.”

Worse yet, a government that changed so frequently would lose the public legitimacy acquired through familiarity and use. Madison believed that a successful constitution could achieve “veneration” by being around for a long time. Indeed, he aspired for the Constitution he had just drafted to achieve that longevity and respect.

Jefferson never replied directly to Madison’s letter. But later in his career, Jefferson advocated for other dangerous constitutional ideas. Angry about Alexander Hamilton’s national bank, which he considered unconstitutional, Jefferson proposed that Virginia make it a crime of treason punishable by death to work for the bank or circulate its currency.

Still later, Jefferson drafted the Kentucky resolutions in response to the Alien and Sedition Act passed by the Federalist Congress and signed by John Adams. He claimed that the Constitution was no more than a compact between “co-states,” and that the states therefore had the right to nullify laws that they deemed unconstitutional.

Madison, seeking to moderate Jefferson’s extremity once again, drafted the Virginia resolutions at the same time. He was careful to restrict the states’ right to declaring that a law was unconstitutional — not refusing to apply it. And he made the distinction still more clear in subsequent writing.

Jefferson loved a good revolution, whether it was the virtuous American or the ultimately not so virtuous French. He cheered occasional rebellion and famously believed that a little revolution was necessary every so often. Madison’s pioneering constitutional vision recognized that pure revolution was anathema to successful constitutionalism. Luckily for us, his vision prevailed.

Noah Feldman is a professor of constitutional and international law at Harvard University and a Bloomberg View columnist.