Discussion Arcs for Topics and Philosophers

Let's define a discussion arc in philosophy as a curve displaying how frequently a term appears in philosophical journal abstracts, titles, and keywords. Discussion arcs can reveal trends over time, as they come and go.

For example, "ordinary language" was a popular topic of discussion in the 1960s:

[click to enlarge and clarify]

My method: I searched for the term in the abstract, title, or keywords (subject) of articles in Philosopher's Index, in five-year chunks from 1940-1945 to 2021-2025.[1] I then divided the number of hits by a representative universe of hits for abstract or title containing "language", "epistemology", "mind", "metaphysics", "ethics", "moral", "political", "aesthetics", or "logic".[2]

By looking for distinctive terms or phrases connected to particular arguments, we can also track when an argument receives wide uptake. For example, Hilary Putnam's famous "Twin Earth" thought experiment, though originally presented in 1975, didn't receive much immediate uptake, receiving peak discussion in the 1990s:

We can also look for topical trends. If you think artificial intelligence is recently hot, you're right!

The figure also shows a smaller peak in the late 1980s, before the "AI winter" that has recently thawed.

Another thing you might see in the artificial intelligence arc, if you squint, is noise early in the data. This makes sense, since the early data have far fewer hits in the representative universe of articles containing one of the nine keywords: 457 articles in 1940-1945, compared to 33,552 in 2016-2020.

We can also examine the discussion arcs of particular philosophers. Note that "discussion" in the sense I've defined is very different from citation. A philosopher who is cited in passing might have very little influence on the shape of an article. In contrast, if a philosopher's name is explicitly mentioned in the title, abstract, or keywords, that philosopher's work is among the chief topics of the article. Discussion rates and citation rates thus capture different phenomena and will sometimes diverge.

Here are the arcs for the seven "most important Western philosophers of all time", according to a poll by Brian Leiter in 2017.

Notice how much discussion there was of Aristotle in the early 1940s! "Aristotle" alone gets more than a quarter as many hits as the broad disjunctive search for "language" or "epistemology" or "mind" or "metaphysics" or "ethics" or "moral" or "political" or "aesthetics" or "logic". Plato and Kant each also get almost as many as Aristotle.

Since then, there's been a steady decline in the proportion of articles mentioning these prominent historical figures. My sense is that this is due to two factors: first, the decline in the relative prominence of history of philosophy compared to other areas of philosophy; second, a shift within history of philosophy toward considering a broader range of traditions and figures, including non-Western traditions and women philosophers.

It's perhaps also interesting that Kant has declined less than the ancient Greeks, overtaking them as the most discussed philosopher.

I thought I'd finish today with discussion arcs of some more recent historical figures, who peak at different times:

Notice that Russell peaks in the 1940s to 1950s, during which period he is discussed almost as much as Aristotle, Plato, and Kant, who themselves are (as I noted above) discussed in a striking proportion of articles. There is a little false positive noise for Russell (some other people with "Russell" as a first or last name), but my estimate is that about 90% of hits are accurate.

Wittgenstein peaks in the late 1960s, Frege in the early 1980s, and Nietzsche in the early 2000s. Heidegger's influence is moderately steady from the late 1960s to the early 2000s, declining modestly in the past couple of decades.

Perhaps worth mentioning: These data cover a wide range of journals, regardless of prestige. In an analysis a few years ago, I found that the journals conventionally regarded as prestigious mention prominent "analytic" philosophers such as Frege, Wittgenstein, Quine, Chisholm, and Putnam much more frequently than prominent "Continental" philosophers such as Nietzsche, Heidegger, Sartre, Foucault, and Derrida: The analytic/Continental divide is alive and well. There might be other interesting trends to discover if we subdivide the universe of articles.

In a week or two, I'll do a follow up post looking at the discussion arcs of prominent philosophers born 1900-1945, partly to test my "age and fame" hypothesis: that philosophers tend to have their peak influence around ages 55-70.

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[1] The data begin in 1940, so I used a six-year chunk for the first period. As of Feb 27, data for 2025 are only about two-thirds complete and there are no data for 2026.

[2] This is not all articles, especially in the early period, where abstracts are less available. The idea is to roughly compensate for having fewer abstracts, and thus fewer opportunities for hits in the early data, by comparing the rate of appearance of the target terms with the rate of appearance of several, but not too many, widely used terms across a variety of philosophical topics.

The Ghettoization of Nietzsche

A major sociological divide in recent Anglophone philosophy is the divide between philosophers who see themselves as working in the tradition of Nietzsche, Heidegger, Foucault, and Derrida -- so-called "Continental" philosophers -- and those working in the tradition of Frege, Russell, Wittgenstein, and Quine -- so-called "analytic philosophers". The labels are problematic and the divisions not always clear, but plainly there's a non-trivial sociological division here. This division is reflected, in part, in journal citation patterns. You might wonder about this history of this. Was Philosophical Review always allergic to Nietzsche? Or is that a relatively recent phenomenon? And how extreme is the phenomenon? Do leading Continental figures get at least some play in the top analytic journals, or are they almost entirely excluded?

Let's look at this quantitatively.

The "Big Three" Anglophone philosophy journals -- all of which have been leading journals since the first decade of the 20th century -- are Philosophical Review, Mind, and Journal of Philosophy (formerly Journal of Philosophy, Psychology, and Scientific Methods). All currently seem to lean heavily "analytic". Also, all are also indexed in JStor, along with a diverse group of 93 other philosophy journals, many of which are not as sociologically aligned with the analytic tradition. So I have looked, decade by decade, at the rates at which the names of central analytic and Continental philosophers appear in these "Big Three" journals compared to other journals.

Compare, first, Nietzsche and Frege -- foundational figures for both traditions, both born in the 1840s. The crucial measure is the rate at which each is cited in the Big Three vs. the rate at which each is cited in the remainder. For methodological details see this note.* For a clearer view of the charts below, click them.

As you can see, apart from a difference for Nietzsche in 1900-1909, through the 1940s or 1950s the Nietzsche lines stay more or less together and the Frege lines stay more or less together. The dashed and solid lines are clearly separated in the 1970s, after which the separation seems to continue to slowly increase. Particularly remarkable is the fact that in the 1990s-2000s, although the terms "Frege*" and "Nietzsche*" appear approximately as often in journals outside the Big Three, there's a huge difference in how often they appear in the Big Three. Over those two decades, the term "Nietzsche*" appears 20 times total in the Big Three, or about once a year total among the three journals, a citation rate of 1.7% -- compared to 7.2% outside the Big Three.  (For Frege it's 24.1% vs. 10.6%.)

A similar story holds for Heidegger and Wittgenstein -- leading early figures in the Continental and analytic traditions, respectively -- and both born in 1889.  (Again, click chart for clarity.)

Despite being cited in over 5% of articles outside the Big Three, the word "Heidegger*" appears only 16 times in the Big Three from 1990-2009, or in 1.3% of the articles.

Okay, how about the Continentals Sartre (b. 1905), Foucault (b. 1926), and Derrida (b. 1930) vs. the analytics Quine (b. 1908), Chisholm (b. 1916), and Putnam (b. 1926)? The graph is a little crowded but the following should be evident: The muted-color analytics show higher in the Big Three (solid lines) than in the remaining journals (dashed lines), while the bright-color Continentals show the reverse pattern -- and the spread is much more evident in the past few decades than it was mid-century. (There's a bit of false-positive noise for Foucault and Putnam, but not enough to mask the general trend. Russell I have chosen to exclude entirely due to false positives.)

Combining the five analytic and five Continental philosophers in a disjunctive search (Frege or Wittgenstein or Quine or Chisholm or Putnam vs. Nietzsche or Heidegger or Sartre or Foucault or Derrida; no wildcards) yields the following aggregate result.

The trends started rapidly pulling apart in the 1950s through 1970s and have continued to slowly pull farther apart since then.

Here's another way to look at it: For any philosopher or group, divide the percentage representation in the Big Three by the percentage representation in all the remaining journals. This yields an index of proportionally how much the Big Three favor that person or group compared to other journals. Call this the "Big Three favor ratio". Unity would mean equal representation in the Big Three vs. the other journals.

The favor ratio of about 1.5 for the analytics over the past couple decades means that the five sample analytic philosophers are about 50% more likely to be cited in the Big Three journals than in other journals. The favor ratio of about 0.2 for the Continentals means that they are about five times more likely to be cited in journals outside the Big Three than by the Big Three.

In the 1990s and the portion of the 2000s that has so far been indexed in JStor, the words Nietzsche, Heidegger, Sartre, Foucault, and Derrida appeared in 45 articles total among 1209 Big Three journal articles (3.7%). Thus, the Big Three journals have included, on average, about one article per journal per year that even passingly mentions any of these five authors.

(On the word "ghetto" in the title of this post: I mean it only to refer to the average Anglophone philosopher's perception of what counts as an elite journal. See, for example, this poll. It is not intended as a personal judgment about journal quality.)

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*Percentages are divided by a representative universe of articles hitting search terms philos* or ethic* or mind*. Only English-language articles are included. Reviews and minor documents are excluded by limiting the results to "articles" in JStor and also by excluding articles with a variety of titles such as "books received", "front matter", "back matter", etc. Without these exclusions the results reported above look very different. For example, not using such exclusions raises the occurrence rate of Nietzsche in the Big Three in the 2000s from 1.3% to 12.0%. Although the search terms run through 2009, JStor only covers through the mid-2000s for many journals, including the Big Three.

Chinese Philosophy Discussion Arcs

Different classical Chinese philosophers have drawn different amounts of discussion in the Anglophone world over the past seventy years.  I want to look at this phenomenon quantitatively and then suggest a general conjecture about the history of philosophy.

The six target philosophers include two who are well-known in the Western world outside scholarly circles, Confucius and Laozi (aka Lao Tzu), and four who are much less well known, Mencius, Zhuangzi, Xunzi, and Mozi (aka Mengzi, Chuang Tzu, Hsün Tzu, and Mo Tzu).  Below is a graph of their "discussion arcs" -- that is, the rates, times 1000, at which their names appear in keyword (including abstract and title) searches in Philosopher's Index, divided by a representative universe of articles. Click the image for a clearer view.

(For more details on discussion arcs, see here and here. My search terms also included many less common early spellings such as Mocius and Chuangtze.)

One result that jumps out is (as one might expect) the relative prominence of Confucius. Also striking, though, on closer inspection, is another phenomenon: The relative decline of Confucius and Laozi compared to the other four philosophers. To better display this trend, here's a comparison of the proportion of articles mentioning Confucius or Laozi to the proportion mentioning any of the other four. (Again, click for clarity.)

I don't interpret as meaningful the apparently very tight match of the lines at the end of the graph -- but the approximate match does seem meaningful. In the 1940s-1970s, Confucius and Laozi combined received about twice as much discussion as the other four philosophers combined. Starting in the 1980s or 1990s, that situation changed.

My general conjecture is this: As a subfield in the history of philosophy matures (as I believe the history of Chinese philosophy has done in the past couple decades), proportionately less expository attention is devoted to the most famous headline figures and proportionately more attention is devoted to less well known figures. This is a kind of "winnowing of the greats" in reverse.

If that conjecture is correct, we ought to see the same effect in other subareas of the history of philosophy.

Discussion Arcs of APA Presidents from the 1970s

One of the highest forms of recognition a philosopher in the U.S. can receive is the presidency of an APA division. Lists of the APA divisional presidencies thus provide information, not filtered through current lenses, of people who were regarded as prominent philosophers in their day.

If, like me, you have a kind of morbid curiosity about the fleetingness of academic fame, you might wonder what becomes of these divisional presidents. Lists from the 1930s and 1940s are almost entirely names I don't recognize: Albert Perly Brogan? Marten ten Hoor?

In several past posts, I have used the concept of a "discussion arc". A discussion arc for a topic or a philosopher is simply the number of times the topic or philosopher appears in a keyword search (including title and abstract) in the Philosopher's Index, divided by some representative number of the universe of articles. Some topics and philosophers have fairly steady rates of discussion over the decades (dualism, Kant); others show sharp temporal peaks (ordinary language, Chisholm). I have found that, in general, twentieth century Anglophone philosophers' discussion arcs tend to peak at around age 55-70.

The three divisions (Eastern, Central, Pacific) had a total of 30 presidents in the years ending 1970-1979. I excluded from analysis nine presidents with last names generating too many false positives in keyword searches.[note 1] Of the 21 remaining presidents, six achieved discussion rates of over five per thousand articles (from a representative universe of articles [note 2]). For analysis, discussion is broken into five-year chunks. Click for a clearer view of the figure below:

Around 1975, most of this group had similar discussion rates (though John Rawls rather more). Most arcs show the typical hump shape with peaks at around ages 55-70. The declines of Jaakko Hintikka and especially Norman Malcolm (both of whom peaked a bit young) are notably more severe than the others.  Rawls and Wilfrid Sellars show bimodal distributions, with the typical late-career peak followed by a more recent resurgence.

A second group of five philosophers had peak discussion rates between 1.5 and 5 per thousand (again click for clarity):

Although the data are noisier, as one might expect with fewer data points, all five show the typical hump-shaped arc, though Stuart Hampshire peaks a bit earlier than typical and Alan Gewirth a bit later. Paul Grice appears to have had considerably more staying power than the others, though his recent discussion rate of about 1.5 remains lower than all in the first group except Hintikka and Malcolm.

Four more 1970s APA divisional presidents, while peaking below 1.5, still continue to draw a bit of discussion, with William Alston and Patrick Suppes recently exceeding all in the mid-tier group except Grice.

Finally, there's a group of six who together have drawn only three keyword hits since the year 2000:

Could we have predicted these results in the 1970s? Yes! If we average the discussion arcs of the four tier groups, the overall trend is clear: The much-discussed remained much discussed, the less discussed remain less discussed:

In fact, the decline is much less sharp, on a percentage basis, for the Tier 1's than for the lower tiers, which might be partly explained by my hypothesis about the Winnowing of Greats.

The spread also seems to be clearly evident by the early 1960s, when these philosophers were in their early 40s to early 50s -- maybe even earlier. We can to a substantial extent predict discussion rates in the 2000s, among APA division presidents from the 1970s, based on those presidents' discussion rates in the five-year span during which they turned 45. If we rank their age-mid-40s discussion rates and also rank their discussion rates since 2000, the ranks correlate at r = .59 (p = .006). Nine of the 21 are ranked very near their age-mid-40's discussion ranks (within 2) and 13 are within 4. The biggest outliers are Malcolm (fell from 2 to 12), Donald Davidson (rose from 12 to 2), and Grice (rose from 14 to 5).

Notes:
1. William Thomas Jones, John Wisdom, Lewis White Beck, Alonzo Church, William Henry Hay, Ruth Barcan Marcus, Kurt Baier, Wesley Charles Salmon, and William Craig.  Also: I hand-culled false positives in any five-year period in which the target philosopher generated 40 or fewer keyword hits on a truncation-symbol appended version of his last name (e.g., Lazerowitz*); for those with 40 or more keyword hits, I spot-checked for problematic patterns.

2. Search term: KW=ethic* or KW=moral* or KW=politic* or KW=language* or KW=epistem* or KW=mind* or KW= metaphys*.