Bill Viola has created a powerful modern altarpiece for St Paul’s Cathedral that perfectly suits the restrained spirituality of this most English of churches.

Coming into Christopher Wren’s great building on a weekday morning when crowded buses surround this London icon, you notice how ascetic its atmosphere is. Greek mosaics and the perfect geometry of a dome that suggests the clockwork universe of Wren’s contemporary Isaac Newton make St Paul’s a place of cool, even philosophical, prayer.

Bloody martyrdoms, harrowing images of saints being crucified upside down or tortured with hot pincers – such gut-wrenching pictures are deliberately sidelined in the temple of reason that is St Paul’s. At least, they were untilAmerican visionary Viola unveiled his latest work, a permanent video installation, there on Tuesday.

Link to video: Bill Viola’s second coming: watch the eerie video installation Martyrs for St Paul’s CathedralIt has taken more than a decade to agree on, plan and install Viola’s eerie multiscreen work Martyrs (Earth, Air, Fire, Water), a quest that started when the cathedral’s overseers were struck by his exhibition The Passions at the National Gallery in 2003. This exhibition revealed the depth of his interest in traditional religious art. St Paul’s has a steady programme of commissioning modern works but there simply is no other artist today of Viola’s quality who is so committed to the idea of religious art. He is making a second work for St Paul’s, to be unveiled next year, called Mary. He says he hopes the pieces are not just art but “practical objects of traditional contemplation and devotion”.

Martyrs is a study in suffering and redemption. Four people on four vertical screens undergo extreme fates: one has been buried, another hangs with her wrists and ankles bound, another sits amid flames and a fourth hangs upside down as he is drenched in cascades of water. As these images develop and transform in parallel, it becomes hard to know what is death and what is hope. Soil is whirled off the buried man in an upward band of dust, like the zip in aBarnett Newman painting, until he is born again, looking up into heavenly light. Similarly, the suspended woman endures her pain to raise her eyes to that light in a final deathly pose of triumph.

Water … Martyrs by Bill ViolaFrom one point of view, Viola has given the Church of England a visceral shot in the arm, a healthy dose of baroque religious art, a blast of hi-tech Caravaggio. His installation is not literally an altarpiece, but a carbon-steel frame containing four plasma screens that irrestibly evoke medieval polyptych altar paintings. It is subtly situated at the end of an arched aisle with a vista that draws you gradually towards it.

This is no shocking gorefest, despite a sado-masochist suggestiveness that nicely challenges clerical banalities (occasionally looking at these bound bodies I thought of Robert Mapplethorpe‘s photographs). Rather, Viola transforms the idea of martyrdom from some horrific intestine-spilling scene that might terrorise a south Italian church into something eerily still, silent and thought-provoking.

Earth … Martyrs by Bill ViolaHis martyrs do not scream or bleed or even pray. They silently endure their strange fates. The stress is not on numbing details of torture – the man engulfed by fire is not singed. It is on the mystery of human courage that can endure the impossible. Is such strength god-given? Where then does it come from? Viola gets to the core of what martyrdom means. Through video art, he reframes the philosophical questions it has raised ever since Socrates refused to escape his unjust execution in ancient Athens.

Martyrs fits beautifully into the cerebral ambience of St Paul’s because it invites you to contemplate what it is to die for a cause, in much the same intensified yet sombre way one contemplates the mysteries of space and time while looking up into Wren’s Newtonian dome.

Bill Viola is one of the most important artists of our time because he has the bravery to engage with these big questions, and the clarity to do so in a universally compelling way. Atheists have not yet built any special spaces for this kind of deep art, so a church is a fine place to see his work. He takes his spot in St Pauls with becoming modesty and genuine profundity.