The result is not a coherent whole: it is really two very short works shoe-horned together, probably because the originating idea turned out to be insufficiently substantial. The biographical material is interrupted by a central section summarising the main strands of Descartes’s philosophical and scientific theories, and the controversies they aroused. Thus we are introduced, in the opening four chapters, to the famous painting (and its original) and, in order, the philosopher, the priest and the painter; this is followed by three chapters on Descartes’s intellectual output, in which the priest and painter are eclipsed; and then a final chapter on the various images of the philosopher, and the roles of the priest and the painter in their genesis.

Lack of coherence does not, however, mean lack of interesting material: Nadler has produced an enjoyable volume with a number of surprises. The first surprise is that the familiar portrait, hanging in the Louvre, is now recognised not to be by Hals at all. It is a copy, ‘after Hals’, and the Hals it is ultimately after is a smaller, more roughly composed painting in the National Gallery of Denmark in Copenhagen. It is this genuine Hals that testifies to the personal links that Nadler investigates in his opening and closing chapters.

The philosopher was a Frenchman, but, in the spirit of his personal motto, ‘the hidden life is best’, he lived most of his productive life in the Netherlands, well away from the dangers of the Inquisition and the intrigues of Paris. Initially (from 1629), he lived in and around Amsterdam, but from 1637 until his fateful departure for Sweden in 1649 (where the severe winter caused him to succumb to pneumonia early the following year), he lived and worked in various small towns near Haarlem and Alkmaar.

It was there that he met the priest. Augustijn Bloemaert was a Haarlem native who was ordained a Jesuit priest in Antwerp in 1611. An independent-minded man, he had a series of run-ins with his superiors and ultimately left the Jesuits to become a secular priest, ministering to Haarlem’s sizeable Catholic minority. He seems to have met Descartes through his friend Johan Albert Ban, with whom Descartes shared an interest in music theory. Ban was a capable harpsichordist (but less successful composer), and he and Bloemaert would meet with Descartes for social and musical evenings to while away the long Dutch winter evenings.

Descartes had formed no intention to leave his small Netherlands community, but in the end he was unable to refuse a request from Queen Christina of Sweden (seconded by the French government’s representative there) to attend her court and instruct her in his philosophy. It was in response to this development that Bloemaert commissioned a portrait of his departing friend.

Frans Hals was Haarlem’s most famous portraitist, and so it is probable that the Hals portrait in Copenhagen is the one Bloemaert commissioned. (Bloemaert was independently wealthy, and already in possession of several Hals paintings, so would have had some connection to the painter.) The Louvre painting is not an exact copy, instead showing similarities to two engravings, at least one of which is independent of the Hals painting. But all are sufficiently resembling to count as reliable, if rough, guides to Descartes’s actual appearance.

What of the philosophical chapters? Nadler provides an admirably clear account of the main lines of Descartes’s thought, and what made it so distinctive and controversial. It was the condemnation of Galileo that led to the works for which Descartes is now best known, the Discourse on Method (1637) and the Meditations on First Philosophy (1641). Descartes had been working on a comprehensive account of the world in mechanical terms, in which a sun-centred cosmos was a central assumption. News of the condemnation led him to abandon the book, if not the project. He decided to publish only some of the safer elements of the work, and to preface it with a sort of intellectual autobiography. This was the Discourse – the source for that famous utterance, ‘I think, therefore I am.’

Descartes had hoped that the Discourse would establish his bona fides, but instead it provoked considerable criticism – especially for its briefly sketched arguments for belief in God, which were alleged to be so weak that they proved him an atheist. Descartes was not a pious man, but he was certainly a religious believer, so these attacks forced him back to the drawing-board. The result was the Meditations, a carefully argued work in which close attention to the religious metaphysics of the day is plain.

The work is modelled on Plato’s allegory of the cave, and just as that famous allegory portrays human existence as lost in ignorance so long as it relies on the senses, and attaining enlightenment only by turning to the realm of pure intellect, thereby to discover the divine, so the Meditations lead the meditator from an all-encompassing doubt to the discovery, first, of his own existence as a rational being, and, ultimately, to the secure epistemic foundation provided by discovering the existence of a perfect (and so non-deceiving) God.

Ever cautious, Descartes sought to cut off possible denunciations at the root, by gathering a selection of responses from notable theologians and philosophers, together with his replies, and publishing them together with the Meditations. This approach was reasonably successful; so, emboldened, he published his Principles of Philosophy (1644), a complete account of his system in textbook form.

Controversies steadily grew in the later 1640s, not least because of the provocations of some zealous disciples. These particularly concerned the implications for religious doctrines, and Nadler does a good job of summarising the issues. However, perhaps overly mindful of predictable sensitivities in the modern reader, he is less comfortable in his handling of the fundamental role Descartes allocates to God as ultimate epistemic guarantor. The fact is that Descartes’s doubt is at this point still relevant: if we are creatures evolved through chance processes, on what basis do we suppose that our intellectual powers are truth-directed? Unless we can answer that question, we cannot guarantee that our scientific theories are genuinely true, rather than merely useful. This is one respect, at least, in which Descartes presents an ongoing challenge to the modern philosopher.

Who is the book for? Its lack of internal coherence may suggest it has two incompatible prospective audiences, but a more positive assessment is possible. All those who remember when, as undergraduates, they found themselves confronted by startling questions about dreaming and existence posed by a long-dead Frenchman whose heavy-lidded gaze stared out at them from the cover of their textbook, and who never quite figured out who he really was or what he was up to, will find many of their questions answered in this compact volume.