digital dualism
n. The belief that online and offline are largely distinct and independent realities.
Other Forms
As someone who runs social media workshops in universities, I’ve become ever more convinced that many of the confusions which surround digital activity stem from a basic ontological misunderstanding of what online activity is. It’s too frequently construed as something distinct from the 'real’ world.

The reasons for this distinction, which has pithily been named digital dualism, are a fascinating question in their own right.
—Mark Carrigan, “Some quick thoughts about sociological realism and digital life,” The Sociological Imagination, June 29, 2012
I agree with most everything he says in the column because, besides the last paragraph, his column is a antidote to digital dualism—the idea that online and offline worlds are somehow separate entities, one "virtual" and the other "real." But his column brings back digital dualism at the end—and does a disservice, in my opinion, to the rest of his points.
—Zeynep Tufekci, “Breaking Bread, Breaking Digital Dualism,” Technosociology, February 08, 2012
2011 (earliest)
The power of social media to burrow dramatically into our everyday lives as well as the near ubiquity of new technologies such as mobile phones has forced us all to conceptualize the digital and the physical; the on- and off-line.

And some have a bias to see the digital and the physical as separate; what I am calling digital dualism. Digital dualists believe that the digital world is "virtual" and the physical world "real."
—Nathan Jurgenson, “Digital Dualism versus Augmented Reality,” Cyborgology, February 24, 2011
A short essay called Digital Dualism that Google claims was published on January 31, 2001, comes close to the ideas behind the phrase as I'm defining it here, but doesn't quite get there, so it's not the earliest citation of the phrase.