There was a time when every self-respecting egghead had to keep up with the latest developments in philosophy; not any more. Today’s intellectuals, if they do not ignore philosophy entirely, can content themselves with reading one or two books about its past. Hundreds of histories of philosophy are available, and they are all much the same: they tell the same basic story, with the same cast of leading characters.

Act one: ancient Greek philosophy, where Socrates postulates an ideal world of which our own reality is but a shadow. Act two: modern European philosophy, which begins in the 17th century when René Descartes tried to cast doubt on everything, thus precipitating a civil war between rationalists who thought that knowledge is based on reason, and empiricists who said that it depends on experience. Act three: professional philosophy, in which Immanuel Kant’s investigations into the logic of philosophical disagreement set it on the path to becoming an introverted technical specialism, increasingly subservient to the natural sciences. The details of the plot may be vague but the message is clear: philosophers are very clever, but very stupid too, promising much and delivering little. Philosophy is history, LOL.

Anthony Gottlieb will have none of this. He is on a mission to show that the great dead philosophers have been misunderstood and that they deserve to be taken seriously. “It is because they still have something to say to us,” he says, “that we can easily get these philosophers wrong.” In 2000 he published The Dream of Reason, a brilliant retelling of the story of ancient Greek philosophy which brought out the lasting relevance of Plato’s idea that truth, happiness and virtue are inseparable, while vindicating Aristotle as a serious thinker about nature, art and society. The Dream of Reason is now joined by this much-anticipated sequel, which picks up the story with Descartes and carries it forward to the beginnings of the French Revolution.

If rationality was the theme of the earlier volume, the present one focuses on novelty: in the 17th century, as Gottlieb puts it with characteristic panache, philosophy started to be dominated by “the new idea that all old ideas are suspect”. Descartes is famous for trying to make a fresh start with his slogan “I think therefore I am”, but no one is sure what he meant, and according to Gottlieb he has been “widely misunderstood”. Gottlieb takes issue with Prince Charles and Pope John Paul II, among others, for presenting Descartes as a “subjectivist”, who got modernity off to a bad start by trying to make the “I” the foundation of everything.

He also rejects the view of Descartes as a “rationalist” who refused to acknowledge the significance of the empirical sciences: he was, on the contrary, a bold advocate of the principle that physical phenomena are generated by the mechanical interactions of tiny particles. On top of that, Gottlieb dismisses stories about a battle between rationalists and empiricists as a “myth”, peddled by 19th-century philosophers with a definite agenda of their own.

Dozens of other myths get their comeuppance in this well-written and fast-moving book. If you assumed that Thomas Hobbes was an atheist who took a gloomy view of human nature, you will have to think again, and if you thought that Jean-Jacques Rousseau believed in a peace-loving “noble savage” you could not be more wrong. John Locke too is “often misunderstood”: he has a reputation for preferring “experience” to “innate ideas”, but his main point was that the mind is not a passive receptacle but an independent agent in the construction of knowledge; and in spite of being celebrated as the architect of modern liberties, he was far from being a liberal, “even by the standards of his own times”.

Meanwhile Baruch Spinoza’s attempt to equate God with nature comes out looking both attractive and plausible, and we learn that when Gottfried Leibniz spoke of everything being “for the best in the best of all possible worlds” he was not denying that life can be bloody awful, but simply reminding us that there is not much we can do about it.

David Hume never took himself too seriously: he performed high-risk philosophical manoeuvres with unflagging good humour

Gottlieb concludes with an affectionate portrait of David Hume, who, as he observes, has become the role-model of choice for philosophers in the 21st century. Hume was a “naturalist”, it seems, who took pleasure in presenting human beings as little more than animals with an inflated sense of their own importance. He also had an enviable talent for “disturbing the peace”, philosophically speaking. But his principal achievement was that he never took himself too seriously: he performed high-risk philosophical manoeuvres with unflagging good humour, and was always willing to concede that his hard-won theoretical convictions might turn out to be ridiculous foibles. If you are upset by abstract arguments, he said, then you should get out a bit more and engage with “common life”, and after a while you will be able to relax as you watch them all “vanish like smoke”.

Gottlieb has got Hume’s geniality down to a T. “Every philosopher likes to think he has reached his conclusions via rigorous reasoning,” he says, with a collusive wink to his readers; in the 17th century, indeed, “falling in love with geometry seems almost to have been an occupational hazard”. Take Descartes: he was notable for “his faith in his own unusually bright light of reason”, but “perhaps he did not have all the answers”. As for Hobbes, he was so “bedazzled” by a priori geometry that he “got rather carried away” and ended up “over-egging his pudding”. But Leibniz is the one you really have to watch, since, poor fellow, he “did, in effect, tend to confuse his own mind with that of God”.

After a while, the jovial put-downs start to sound mean-spirited. It is fine to be diffident about one’s own powers, but there is something sneaky about being diffident on behalf of others, and Gottlieb risks undermining his defence of the great philosophers by depicting them as incorrigible fantasists, lost in their dreams of reason and enlightenment.

He tells us he is already at work on the final volume of his trilogy, which will run from Kant to the present, and the book will be eagerly awaited. But let’s hope that he will rein in his Olympian irony, and start treating his heroes with a little more respect.

• The Dream of Enlightenment: The Rise of Modern Philosophy is published by Allen Lane. To order a copy for £16.40 (RRP £20) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.