KEYNES by Robert Skidelsky. RUSSELL by A C Grayling ERASMUS by James McConica, NIETZSCHE by Michael Tanner, AUGUSTINE by Henry Chadwick, MACHIAVELLI by Quentin Skinner, ROUSSEAU by Robert Wokler, SCHOPENHAUER by Christopher Janaway, MARX by Peter Singer PAUL by E P Sanders PAST MASTERS, edited by Keith Thomas. Oxford University Press Pounds 5.99 each

Ronald Hayman looks at introductions to thinkers and their ideas. How much can be taught in an hour and a half about Plato or Descartes (or Hume or Wittgenstein) to sixth-formers who have never heard of him? This optimistic new series by Paul Strathern demonstrates that the answer is “Quite a lot”.

Containing less than 80 pages with only 22 lines of large print on each page, each book really can be read in less than 90 minutes without scampering through the argument too fast. An investment of six hours in the four books could instil a healthy curiosity about philosophy and its history.

But jokey, chatty sentences that might pass muster in a classroom or on a television programme can look bumptious and inadequate on the page. “Plato was a well-known wrestler, and the name by which we know him was his ring name”. Half-truths are sometimes acceptable, but too many of Paul Strathern’s statements are less than half true. For instance, “Hume is the only philosopher whose ideas remain plausible to us today”. Sometimes, when he tries to be breezy, the breeze consists mainly of hot air: “Descartes and the rationalists make us realise that the human condition is not rational; the earlier empiricists seem either self-evident, wrong-headed or absurd.”

Had they written more intelligently, these four books would have been useful in the classroom, but they’re full of statements that no good teacher would accept from a pupil. It can’t be said that “nothing original happened” in philosophy for nearly 2,000 years between Aristotle and Descartes. Sartre, who was arguably the last important existentialist philosopher didn’t “instigate” existentialism when he published Being and Nothingness in 1943.

And to pupils who are still justifiably tentative about drawing a boundary between philosophy and literature, it’s invidious to say that “unfortunately”, Plato’s use of an image - the cave - to explain his Theory of Ideas “puts this in the realm of literature rather than philosophy”.

In comparison with these 90-minute books, the seven reissues in the Past Masters series are all long books, with more than 100 pages and about 40 lines of smallish print on each page. The two new additions to the series, Keynes, by his biographer, Robert Skidelsky, and Russell, by A C Grayling, are both exemplary in covering difficult subjects with lucidity and concision. As summed up on the blurb, the intention is to present in all 60 “concise, lucid, authoritative introductions to the thought of leading intellectual figures of the past whose ideas still influence the way we think today”.

It’s debatable whether Jesus, Saint Paul, the Buddha and Muhammad should be described as intellectual figures, and in his interesting book on Paul, E P Sanders is handicapped by the nature of Paul’s greatness, which was not as a thinker but as an evangelist. Certainly, though, the editor of the series, Sir Keith Thomas, was right to include Jesus, the Buddha and Muhammad.

There’s room, of course, for endless argument over the selection of “intellectual figures”. Dostoevsky, Proust, Trotsky, Thomas Mann and the Marquis de Sade are all good candidates. Bach is the only composer Sir Keith has admitted, though it would be hard to deny either that Wagner had ideas or that they still influence us today, less directly, perhaps, than indirectly through the work of other “masters” such as Nietzsche and Mann.

Generally Sir Keith maintains a high standard. He tends more than Frank Kermode did when editing Fontana’s Modern Masters to choose academic contributors, and one of his problems is whether to give them complete freedom in their approach. How should a thinker’s life be interwoven with his thought? Though much less is known about St Paul’s life than Nietzsche’s, E P Sanders gives us more biographical information in his book on Paul than we get in Michael Tanner’s book on Nietzsche. “Nietzsche’s fundamental concern throughout his life”, we’re told, “was to plot the relationship between suffering and culture, or cultures”. But Tanner doesn’t go into detail about the experience that gave the unfortunate Nietzsche his specialist familiarity with suffering.

Another problem for both editors is how to separate past masters from modern masters. Freud, Jung, Gandhi, Heidegger, Russell, Wittgenstein and Keynes feature in both, but, since we’re dealing with masters, there can’t be too many books on them, so long as the books are good, and these mostly are.

Ronald Hayman’s biography, Thomas Mann, is published by Bloomsbury