The enduring allure of conspiracies

The United States of America was founded on a conspiracy theory. In the lead-up to the War of Independence, revolutionaries argued that a tax on tea or stamps is not just a tax, but the opening gambit in a sinister plot of oppression. The signers of the Declaration of Independence were convinced — based on “a long train of abuses and usurpations” — that the king of Great Britain was conspiring to establish “an absolute Tyranny” over the colonies.

“The document itself is a written conspiracy theory,” says Nancy Rosenblum,...