The complete history of philosophy visualized in one graph

Simon Raper of Drunks&Lampposts has compiled a mesmerizing graph that charts the entire history of philosophy. By extracting information from the "influenced by" sections in Wikipedia, he was able to visually convey an overarching web of philosophical traditions. And by adding extra weight to the most influential philosophers, Raper was able to produce a compelling graph that offers some fascinating insights into the formation and development of various schools of philosophical thought.
The first thing you notice when looking at the graph is that there are six primary philosophers who take center stage in terms of their influence, namely Plato, Aristotle, Kant, Hegel, Marx, and Nietzsche (the last one being a bit of a surprise — though Nietzsche's writings have certainly returned to vogue in recent years).

Conspicuous by his absence is Descartes, but Raper offers a possible explanation: The chart only measures direct influences, and it's likely that Descartes's tremendous contribution has trickled through second and third degree associations. Alternately, it could also be the fault of strictly using associations established by Wikipedia editors.
Other highly influential philosophers (rightly) include Kierkegaard, Husserl, Heidegger, Leibniz, Rousseau, Hume, Wittgenstein, and even Noam Chomsky.
The graph also shows a certain amount of "clumping" that one would expect — a logical grouping of philosophers within their respective traditions, and in close relation to their precursors and eventual offshoots. The ancient philosophers are nicely represented in green at the top-left corner. The continental tradition is shown through the initial grouping of Hegel and Nietzsche, leading into Heidegger and Sarte, and then into the "isms" of the 20th century. The graph also shows the analytic school of Frege, Russell and Wittgenstein, along with the American pragmatists.

What's also very neat about this graph are the outliers. Looking around the edges, you can see some lesser known philosophical schools, including various Arabic and religious traditions. But perhaps most revealing of all is the graph's suggestion that no philosophical movement is an island unto itself; everyone stands on the shoulder of the giant who preceded them.
Be sure to check out Simon Raper's site and browse through the large image he's provided.