The problem occurs, then, when we consumers burrow down into our self-selected spaces within that continuum, drowning out the noise we don’t like in favor of the noise we do. And it occurs even more acutely when we systematize such selective narrowness, writing it into the very DNA of digital journalism. In And Then There’s This: How Stories Live and Die in Viral Culture, Bill Wasik describes the “feedback loop among bloggers and readers,” citing a study finding that 85 percent of blog links led consumers to blogs of the same political bent—“with almost no blog showing any particular respect for any blog on the other side.” In this way, selective exposure becomes a communal activity.

And so, ironically, does cognitive isolation. “If extremism is generated after encountering competing arguments, by all means,” notes the legal scholar Cass Sunstein, who has made extensive studies of crowd dynamics. “The problem is when extremism emerges from the logic of social interactions”—from, in other words, a system of discourse that allows for self-segregation. And that’s the problem we’re seeing, increasingly, in our journalistic infrastructure. On the one hand, people have access to more dissenting views than ever before; on the other, paradoxically, they are more able to ignore those views than ever before. My reality here. Your reality there.

But: what about our reality?

The result, for news consumers, is an increasing permissiveness when it comes to fact itself. Outlets offering different, and often competing, versions of truth—when those outlets have roughly the same scope and sway—suggest, implicitly, an equivalence between those truths. “Political scientists have characterized our epoch as one of heightened polarization,” notes Farhad Manjoo; now, however, “the creeping partisanship has begun to distort our very perceptions about what is ‘real’ and what isn’t…. And it is more convenient than ever before for some of us to live in a world built out of our own facts.”

Proliferation and fragmentation, for all their obvious benefits, also suggest a course toward broad cognitive confusion. How, after all, in a world teeming with multiple versions of reality, are we supposed to know what to believe? In all the white noise, how do we ensure that we’re filtering what we need to hear—as actors, as consumers, as citizens? How do we determine which information will keep us broadly synchronized with the rest of the world? “A man with a watch knows what time it is,” the saying goes. “A man with two watches is never sure.”

Diversity and Democracy

Our political system demands not only that citizens receive a steady flow of information that will, in turn, allow them to be democratic decision-makers—but also that the information in question be, in a profound sense, shared. “A popular Government without popular information or the means of acquiring it,” James Madison wrote, “is but a Prologue to a Farce or a Tragedy or perhaps both.” It’s telling, here, that popular information, shared information—rather than simply information itself—was the founder’s concern. Without “popular information,” we lose not only our baseline of knowledge about the political world, but also our bearings within it. We risk becoming subject, as it were, to subjectivity itself—and ending up with a society, as William James had it, in which “people think they are thinking when they are merely rearranging their prejudices.”

Of what value is discourse, after all, when we’re unable able to talk about, and act upon, the same things? Imagine a book club in which everyone shows up having read different books—one person having read The Brothers Karamozov, another Pride and Prejudice, another Twilight. Or a town hall meeting in which one citizen comes prepared to talk about teacher tenure in the local schools, another to talk about improving a neighborhood park, another to talk about rewriting local zoning laws. There may be some discussion, sure—but that discussion will be crippled to the point of absurdity. Democratic discourse requires the core commonality of shared information; otherwise, what’s the point?

“The idea,” Cass Sunstein puts it, “is that our system at its best is a deliberative democracy. And a deliberative democracy has preconditions. If we celebrate the capacity to self-sort, we’ll lose sight of the value of deliberation.”

Megan Garber is an assistant editor at the Nieman Journalism Lab at Harvard University. She was formerly a CJR staff writer.