James Madison could not have envisioned the internet, but he certainly anticipated the threat of misinformation and polarization to a society. In “Federalist No. 10,? Madison called it the power of “faction,” or extreme partisanship, that “inflamed [men] with mutual animosity” at the expense of the common good. Madison, however, thought that the sheer size of the United States and the deliberative, moderating aspects of the Constitution might make it more difficult for anyone to spread outrage widely beyond their states. Enter technology and its amplifying impact on human instincts. In the 1800s, the telegraph connected far-flung communities with information...