The fame of René Descartes’ phrase “I think, therefore I am”, as well as its overuse and parody, is matched by the endless reproduction and caricature of his portrait hanging in the Louvre. But the French philosopher, who spent most of his adult life in the Dutch United Provinces, never sat for that portrait, nor was it painted by Frans Hals, as has been assumed for a long time. The real Hals portrait, it appears, is not in Paris but in the National Gallery in Copenhagen; a roughly painted little panel, “easily mistaken for a sketch rather than a finished composition”, as Steven Nadler puts it.

To compare Nadler’s book itself to a painting, this is a triptych: Descartes is flanked by the painter Hals and the priest Abraham Bloemaert. The unknown priest from Haarlem is the connection between the philosopher and the painter. According to Nadler, it was Bloemaert who commissioned the portrait on the eve of his friend’s departure to “the land of ice and bears”, upon the invitation of Queen Christina of Sweden to instruct her in Cartesian philosophy. The priest and the painter serve as sidekicks, and put the picture of Descartes in perspective. The accounts of their lives, so different from Descartes’, enable Nadler to paint a detailed portrait of the religious, cultural and political landscape of the Dutch Republic.

The middle panel, of course, gets the most attention. In three consecutive chapters, Nadler takes his reader on a tour of the masterworks of Descartes: the Discourse, the Meditations and the Principles of Philosophy. All famous arguments pass in review: the method of doubt, the dream argument, the deceitful demon, the cogito, and the way the world is built up again from that last indubitable truth. I have read many introductions to Descartes, but I have rarely come across such an attractive display of Descartes’ main philosophical themes. Nadler shows how Descartes’ philosophical and scientific concepts connect, indicating to which end the arguments are put forward.

These well-written chapters make compelling reading. The exposition is vivid, like the painting by Hals in Copenhagen, and adorned with quotes from the correspondence. The fact that Nadler does not delve deep into the mind/body problem is somewhat unexpected, but it isn’t a grievous omission. Descartes himself declared that there are limits to our understanding of the interaction between mind and body – and these limits still exist. The subsequent chapter on God is, after the fireworks in the previous chapters, arguably too much of a good thing. According to Nadler, God plays a central role in Cartesian epistemology and metaphysics, but even if he is right in that claim, it comes as an unexpected turn to the reader, and it does not fit easily into the Cartesian worldview presented earlier.

A 17th-century biographer of Descartes informs us that Bloemaert did not want to let his friend leave “without having him captured by a painter”. Unfortunately, we do not know for sure whether the painter in question was Hals. The biographer does not mention any name, nor is a Hals-painted portrait of Descartes listed in an inventory made after Bloemaert’s death of his many paintings. Nadler is nevertheless able to make a good case for the Copenhagen painting, and I am certain that in due time more clues will be found that strengthen his claim. Would it be important to have the true provenance unveiled? This masterfully painted portrait convinces me it does.