Does this mean that the old idea of a “gentle commerce” of free markets, famously espoused in the French Enlightenment, is dead? Perhaps it never really existed. History shows that free markets can be a basis for friendship between powerful nations, but they are far less successful at securing peace and democracy than many have hoped. In fact, the noble talk of the free market was sometimes simply an excuse to engage in the kind of “great power” competition that too often leads to war and plunder. The idea that trade brings peace has its origins in humanist thought, which...