They might seem an incongruous pair at first, but historically speaking Hieronymus Bosch and Pieter Bruegel the Elder are a natural duo for comparative study. When Bruegel entered the painters’ guild of Antwerp in 1551, Bosch, who had died in 1516, was still the most famous and imitated artist of the age. Antwerp, the centre of European art production at the time, was home to a whole mini-industry of Bosch imitation and forgery, and Bruegel himself cashed in on the continuing demand for his predecessor’s characteristic style. Look at the Boschian pastiches of his ‘Seven Deadly Sins’ series (1558) or 1557’s Big Fish Eat Little Fish, printed with the misleading inscription ‘Hieronymus Bos inventor’, and you can see why a contemporary dubbed Bruegel a ‘second Hieronymus’.

Imitation is not the same as kinship, though, as Koerner is quick to note in this rich and illuminating study of the two painters. Bruegel’s mature style, clear-eyed, intent on the human, temporal and mundane, is a world away from Bosch’s fantasias of the demonic, eternal and infernal. And more fundamentally still, Koerner argues, they belong to two different ages of art history and represent two distinctive conceptions of what art was for. Bosch was a devotional Catholic painter (despite what Koerner pithily calls the ‘rich body of delusional scholarship’ striving to make him a heretic or madman), and he belonged to an age in which artistic ‘subservience to the sacred’ was the norm. Bruegel marks the ‘watershed’ at which European painting ‘emancipated itself’ from that subservience – thanks in no small part to the démarches he himself made. Retrospectively at least, his ‘genre’ scenes of everyday life, his prints and his landscapes seem instrumental in art’s successive migrations from the church to the palace, then to the home and eventually to the museum.

The persuasive case Koerner makes here, however, is that these differences are themselves a philosophical linkage between Bruegel and Bosch. Behind Bruegel’s art of the everyday, Koerner argues, lies what he terms ‘enemy painting’ – the genre Bosch made his own. If, along with mainstream scholarship on Bosch, we read his central subject as the threat of damnation – a threat posed by Satan (‘enemy’ in Hebrew) – the link becomes clear. Where else can Satan threaten us than in our own world? He is supernatural, but his sphere of influence is quotidian. ‘Representations of everyday life and of Satan’, Koerner notes, ‘went hand in hand.’

This insight is good grounds for keeping an eye out for the everyday beneath Bosch’s weirdness – something persistently missed in one-dimensional readings of him as a grotesque painter. It is there in The Haywain and even in his bric-a-brackish hellscapes, but the clearest example that Koerner produces is The Seven Deadly Sins and the Four Last Things, now in the Prado. Here each sin is illustrated in an everyday setting: anger in a brawl outside an inn, pride in a woman’s dressing room, and so on. Joined in a circle, the seven sin-scenes form the white of an eye, around an iris of golden rays, with God in the pupil surveying it all. Beyond the central ‘eye’, the four corners of the panel show what waits beyond the round of sin called life: death, judgement and hell or, if we are lucky, heaven. ‘Beware, beware, God sees’, states the Latin inscription in the inmost circuit of the ‘iris’. Given the geometry of the painting, we are presumably meant to understand that God both sees and sees through our world, just as the wise Christian also should.

Koerner deftly traces this idea of seeing and seeing through the quotidian in Bruegel’s work, too, where it becomes naturalised to the ‘lifeworlds’ of those it represents. Making the link to Bosch’s ‘enemy painting’, Koerner presents Bruegel as an artist who keeps showing us a world littered with pitfalls and snares that those within the paintings themselves are unable to see. In The Parable of the Blind Leading the Blind (1568), we watch the blind beggars walk towards the river, unaware that it has already claimed their leader. In the more complex The Peasant and the Bird Thief (1568), a peasant points out a man raiding a nest to us. This invites our complicity – the peasant brings us into his world – but it also gives us the superiority of seeing what he does not: concerned with getting our attention, the peasant is about to fall into a stream. The same dynamic of ignorance, complicity and superiority occurs again in the tondo The Misanthrope. The legend on the painting, ‘Because the world is so deceitful, I go in mourning’, is likely a later addition, but it serves as a fitting motto for the misanthrope. He does not see the perfidy of the world actually occurring: before him lies a scattering of caltrops; behind him a grinning thief cuts his purse string. ‘Personifying the world’s treachery’, the thief, strangely encased in a metal globe, looks to us as he grabs the misanthrope’s purse, as if sharing a joke. But does he know that he is trapped, first in that strange cage and second within the world itself, represented by the spherical shape of the painting? Bruegel’s work, Koerner argues convincingly, offers visions of everyday life, but is also a type of enemy painting: our privileged point of view on the deceptive worlds of the paintings is a timely reminder of our unprivileged point of view in our own deceptive world.

To boil this book down to a single argument is, though, to miss its real strengths, and certain weaknesses too. Koerner skips too blithely over questions of what works actually belong in Bosch’s oeuvre. A definitive list of genuine works is infamously hard to pin down and the monumental Bosch Research and Conservation Project (BRCP), the findings of which were published in toto last year, has raised new questions about authorship. The issue is vexed by the existence of 16th-century forgeries and by modern institutional resistance to de-attributing famous pieces. Notably, Koerner is silent about the long-disputed authenticity of The Seven Deadly Sins and the Four Last Things, which has been in doubt for over four hundred years. Questions were first raised by the generally reliable Felipe de Guevara in his Commentaries on Painting, written in around 1560, a source Koerner otherwise relies on heavily. Last year the BRCP firmly deattributed it. The Prado, meanwhile, maintains that it is a genuine work. We cannot, I think, know one way or the other, but Koerner’s strategic silence in the service of his argument does not seem the most scholarly response possible.

One could pick out other problems – a few errata in the picture captions, the lack of a separate bibliography, recycling of passages from Koerner’s earlier books – but in the context of the book as a whole they really are quibbles. Bosch & Bruegel is learned, playful and insightful. Above all, Koerner is a brilliant reader of pictures, whose observations, grounded in a lifetime of looking, are animated by a nonchalantly fluent grasp of concepts from aesthetics, philosophy and anthropology. His picking apart of ‘the intricate machinery’ of these paintings is magisterial and intensely enjoyable. Even if, much like Bosch’s nudes, Koerner’s arguments tend on close inspection to be more suggestive than firmly outlined, they remain utterly intriguing.