Gompertz should not be so tentative. He writes with a soft tone, but the people he praises did not. Their own manifestos show them for the violent imposters they were, seeking legitimacy in scandalously fashionable poses. To read what they wrote is to see that their intellectual level was that of the average internet ranter. It is bitter adolescent drivel — even if Gompertz would call Dadaism just an ironic "celebration of childishness". It is artistic extremism (a term Wyndham Lewis used later in life, acknowledging his own guilt), and it is uncoincidentally linked to other sorts of extremism. Gompertz apologises for Futurism's dalliance with fascism, but, unsurprisingly, no apologies are made for Soviet art. For him, revolutionary Russia was fertile for art because it had an "avant-garde intelligentsia".

Really this book has the wrong title. It is a faithful history of avant-gardism, not a history of modern art — if modern art is just the art of the modern period. It is the story of how, because of Duchamp, art went from being something "man-made, typically of aesthetic, technical, and intellectual merit" to being "pretty much whatever the artist decreed it to be". You may, however, not see too much wrong with that older definition, and you may have no interest in an endless game of redefining something that can now, by definition, be anything. 

Gompertz comes out of the Tate, and so does his book. The cover design shows it as well as the argument. Tate Modern is not a museum of modern art; it is a monument to avant-gardism, with all the minor isms inscribed on the wall "in memoriam". As it has gradually given more space to installations, and hidden away its good paintings, preferring radical riddles to refined achievement, so does this book, on 150 years of modern art, manage not to mention the mature work of Bonnard and Matisse, not Beckmann, or any of the other Modernist painters of saner, serious intent, let alone the many milder artists who kept away from the movements altogether. Artworks worth just looking at are largely ignored; apparently, enjoyment of art is not aesthetic, it is only in approving of the artist's politicised attitude. Gompertz sees that today's art world is "more commercial than ever: artists tend not to starve in garrets in the 21st century, several are multi-millionaires... Art today is a business, a career choice." There are plenty still in garrets, painting away, for whom art is no career. They are where the rich avant-gardists were. This book is evidence of how that happened. It is a committed introduction to, and explication of, the Serota tendency. And Sir Nicholas Serota is duly thanked at the end. Duchamp "emancipated art from the darkness of its medieval bunker as Galileo had done for scientific discovery 300 years earlier, enabling it to flourish and unleash a far-reaching intellectual revolution." In which case, we might say: show us back to that darkness, please, from which Raphael and Rembrandt shone so bright.