The Popular Persistence of Fading Philosophers

Late last year, Jean-Baptiste Michel and co-authors made public the Google Books Ngram Viewer, which graphically displays the rates at which words appear in the Google Books database over time. So, for example, one might compare Descartes vs. Nietzsche in English (click to enlarge):

or in German:

Pretty cool! We see Nietzsche (red) overtake Descartes (blue) in English. Plato (green) kicks butt in English, but does much more poorly in German while Kant (yellow) kicks butt in German and only recently challenges Plato in English. (Note: Using "Platon" in German. Merging with "Plato" in German raises Plato to almost the level of Nietzsche.)

Now, earlier in 2010, I had run a series of posts on what I call "discussion arcs", using as my measure the rate at which terms appear in keyword searches in the Philosophers Index database, over time. Naturally, it occurred to me to wonder whether the Ngram would deliver similar results.

It does not.

Some obvious differences are Ngram's broader expanse of time and the difference between the whole universe of books as a database vs. just philosophy sources -- especially the potential swamping of philosophy sources with non-philosophy sources. But even if we confine the search terms to names of philosophers that are distinctive enough so that we can assume that the references are mostly to those specific philosophers, there are important differences between the results.

Here's one: In one post, I noticed that most philosophers tend to have peak discussion in the Philosophers Index around age 55-70, while others (like Heidegger and Wittgenstein) seem to break away from the pack, without slumping in discussion. See these two graphs of fading philosophers:

Interestingly to me, these same "fading" philosophers -- at least the ones with canonical first-last name combos of the sort necessary for Ngram searchability -- do not fade appreciably in the Ngram results (again please click for viewability):

My interpretation: Not only is there an understandable delay between when a philosopher earns discussion by peers and when that discussion spreads into the universe of books as a whole, but there is an even more substantial delay between when philosophical discussion fades and when that fading begins to register in the universe of books as a whole. Philosophy of science is much less about Popper now than it was in the 1970s, despite the Ngram graph. And Josiah Royce? Most contemporary philosophers know him only as someone who used to be a famous American philosopher; few could, I suspect, name even one of his works or positions.

[Updated March 7]