Talking about Twitter the Network is hard. I’ve tried it once before, when my colleague Adrienne LaFrance and I tried to describe how English-language, U.S. Twitter of April 2014 differed from the equivalent Twitter of two years prior. Eighteen months on, I think our effort missed a lot. But I do think we noticed that the social network was slipping into something like midlife. It sometimes feels like Instagram, for instance, is the only social network that people actually still love to use.

But I’m still talking in terms of feel: a biased, decidedly non-precise way of discussing something which emerges from more than 300 million minds. And that’s why I like one theory of what’s changed about Twitter from the Canadian academic Bonnie Stewart. I think it makes clear why Twitter the Company is finding such difficulty attracting new users, especially in the United States. And I think it even helps answer the Instagram question, namely: Why is Instagram (or Vine, or Pinterest) so much more fun than Twitter?

The only problem: To talk about Stewart’s theory, you have to first tackle the ideas of the 20th-century philosopher of media, Walter J. Ong.

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Discussions of Walter Ong always lead off with a litany of job titles. Ong was an English professor and a historian of religion at Saint Louis University. He served as president of the Modern Language Association for a year. He was Marshall McLuhan’s student. And from age 23 to his death in 2003 at 91, he was or was training to be a Jesuit priest.

Ong’s great scholarly focus was the transition of human society from orality to literacy: from sharing stories and ideas through spoken language alone, to sharing them through writing, text, and printed media. His work catalogued the many differences between these two cultures: that orality treats words as sound and action, only; that it emphasizes memory and redundancy; that it stays close to the “human lifeworld.” In literate cultures, on the other hand, words are something you look up; language can stray more abstractly from objects; and speech, freed from memorable epithets like “the wine-dark sea,” can become more analytic. (Am I painfully simplifying a great scholar’s work here? Of course.)

Ong advanced this analysis for modern times, as well. To describe oral communication that was filtered through high technologies like radio and TV—technologies that could not exist without literacy—he coined the term secondary orality. To Ong, secondary orality was one of the great media phenomena of the 20th century.

As the Internet took hold, secondary orality started to sound pretty inadequate. We don’t aurally orate to each other online, after all—we chat, we type, we text. One of the key attributes of orality is its instantaneousness: There’s no delay between utterances, as there would be in a conversation among letter writers or columnizing pundits. Yet online writing often assumes the same instantaneousness. As Ong put it in an interview late in life: Online, “textualized verbal exchange registers psychologically as having the temporal immediacy of oral exchange.” In other words, we process chatty words online (whether on Twitter or Slack or gchat) like we process someone saying them to us in front of us.