To be really smart, though, an online group needs to obey one final rule—and a rather counterintuitive one. The members can’t have too much contact with one another. To work best, the members of a collective group ought to be able to think and work independently.

In other words, if we know a digital tool is going to remember a fact, we’re slightly less likely to remember it ourselves.

As Farhad Manjoo documented in his book True Enough, it isn’t just about opinions—like-minded groups reinforce each other’s lousy, half-true, or even patently wrong facts. This is called selective exposure: we seek out and pay close attention to facts that suit what we believe, ignoring the ones that don’t.

“I do not sit down at my desk to put into verse something that is already clear in my mind,” Cecil Day-Lewis wrote of his poetic compositions. “If it were clear in my mind, I should have no incentive or need to write about it. . . . We do not write in order to be understood; we write in order to understand.”

In “Funes, the Memorious,”

While reading Kasparov’s book How Life Imitates Chess on my Kindle, I idly clicked on “popular highlights” to see what passages other readers had found interesting—and wound up becoming fascinated by a section on chess strategy I’d only lightly skimmed myself.

When tools and institutions emerged to track Americans’ personal data—like the Social Security number or credit bureaus—we passed laws to limit who could see our info and how long it was retained. Artificial forgetting can work if we want it to.

Every new tool shapes the way we think, as well as what we think about.

Viktor Mayer-Schönberger, the author of Delete: The Virtue of Forgetting in the Digital Age,