At the heart of Alan Ryan’s monumental two-volume history of western political thought is a belief that the thinkers it revolves around — Plato, Aristotle, Machiavelli, Thomas Hobbes, Karl Marx — remain relevant,

“Even if they are hard put to explain it themselves to one another,” Ryan writes, “political theorists have no doubt they are engaged in productive, if sometimes frustrating, conversations across the centuries with their long-dead predecessors, as well as their contemporaries.”

What Ryan is getting at is context, the secret story of On Politics, which takes a long view, framing its subjects as the components of a continuum of which we are still a part.

Ryan, who has written books about John Dewey and Bertrand Russell, is well-suited for such an undertaking; a professor and administrator at Oxford, he teaches politics at Princeton and has been working on On Politics for 30 years. The books are a distillation of his thinking, intellectual and practical. Though they can be daunting, the triumph is how, as Ryan takes us through the material, he makes it so much more.

Context, for Ryan, means two things: how his subjects echo one another, and the way they reflect their times. Thus, his take on Plato begins with a portrait of the philosopher as an aristocrat with ties to the oligarchy that “briefly replaced the Athenian democracy at the end of the Peloponnesian War,” a position that influences The Republic and its sense of social hierarchy.

Chapters on modern times are provisional, an attempt to fit large global forces (terrorism, globalization, religious fundamentalism, environmental degradation) into his argument, although he can’t help but focus on broad strokes rather than particulars.

David Ulin reviewed this book for The Los Angeles Times.