One of the more perverse features of social media is that it often produces the opposite of its stated intentions. It claims to bring us closer together; it leaves us divided and angry. It professes to be a transmitter of knowledge; it has convinced your grandfather that Bill Gates is Satan incarnate. And, while social media aims to be a supportive space, its relentless cheeriness often curdles into something sinister—a monomaniacal valorization of good vibes above all else. Now, there’s a term for this singular pursuit of uplifting feeling via Instagram captions that forbid “bad energy” and “the haters”:  toxic positivity.

Toxic positivity did not come from the internet. But its place in the popular consciousness is inextricable from the web. Google searches for the term fi...