Atheism has never come up with anything like the art of 17th-century painter Francisco de Zurbarán, who created a pure and intense religious visual language. I find his images uniquely appealing at Easter – even though I don’t believe in his, or any other, god.

Zurbarán worked in Seville in the days when this Andalucían city created its renowned Holy Week rituals. In his painting Agnus Dei, a trussed lamb, bound for death, symbolises Christ. In The Apostle Saint Peter Appearing to Saint Peter Nolasco, the supposed founder of the Catholic church, appears to a Christian visionary.

Saint Francis in Meditation (1635-39) by Francisco de Zurbarán. Photograph: National Gallery Collection/Corbis

Peter is said to have been crucified upside down – Caravaggio also painted his martyrdom with hallucinatory power. But where Caravaggio makes the upside-down crucifixion happen before your eyes, Zurbarán shows it at one remove: as a vision, a revelation.

This is typical of an artist who expresses, with poetic perfection, the spiritual Catholic revival of the Counter-Reformation era. In 16th- and 17th-century Spain, mystic saints showed new ways of relating to God. Saint Teresa of Ávila and Saint John of the Cross created a personal, ecstatic and soul-searching Christianity.

More than any other artist, Zurbarán conveys the power of Catholic mysticism. His painting of Saint Francis of Assisi meditating, in the National Gallery, is an eerie vision of the self obliterated by prayer. As he contemplates God, it is as if the hooded Francis has literally vanished into a dark abyss. His face can barely be seen. It gradually becomes visible as a shadow, an afterimage. He is lost in the divine.

I became an atheist when I was 15, after a childhood in the church in Wales. For me, Darwin killed God. But I don’t see why my beliefs should stop me admiring religious art, or respecting the experiences that shape it. I recently thrilled at Islamic art in Morocco and at Catholic art in Spain. Atheists have not created anything comparable – there are no rationalist Zurbaráns. The problem with aggressive Dawkins-style atheism is that it rejects huge swathes of history and culture.

So why is it a problem to say that religion has added experience to the world, yet is untrue? Mysticism is noble; so is religious art. I don’t want to deny the value of the great cultural achievements made in the name of religion – or the moral dimension of faith. Religion is a wonderful human achievement. It just happens to rest on implausible fictional accounts of the universe. It’s a nice story, and it created lovely art. Shame it’s all made up.