Can Elon Musk Save Free Speech Online?

Elon Musk, the world’s richest man and most interesting CEO, wants to save democracy. And he is putting his money where his mouth is. A federal securities filing on Monday revealed that Musk has taken a 9 percent stake in Twitter, making the Tesla boss the social-media giant’s single largest shareholder. The move followed several tweets over the past few months in which Musk hinted he is unhappy with the state of free speech on the platform.

Most recently, he tweeted a poll in which he proposed that “free speech is essential...