Morgan Meis in The Smart Set:
El Greco is confusing. He is one of the few universally acknowledged great artists of history who does not fit into any of the established art movements or categories. Given his time period (late 16th – early 17th centuries), his art should fit into the early Baroque. But it does not. One characteristic of all the artists we now call Baroque is a fidelity to the physical presence of bodies. Think of Caravaggio’s light-splashed naturalism, the glow on the cheeks of the young boy-models that he dressed up in all manner of costumes. Or think of Rubens’ fleshy obsession with the might and heft of the human form, the huge canvases like giant meat towers made of bodies laboring at some common task.
El Greco, by contrast, painted unnatural bodies. They aren’t the sorts of bodies that exist in this, our world. El Greco’s bodies are longer and stretchier than those we encounter in daily life. He portrayed the human form as you might see it in a vision or a mystical trance. He looked at painting, it would seem, in the same way that his contemporary — the great mystic Saint Theresa of Ávila — looked at prayer. They were both seeking spiritual ecstasy.
Except, there is no evidence that El Greco had any interest in spiritual visions or mystical ecstasies. Instead, he read boring tracts of Counter-Reformation theology and studied Renaissance art theory (we still have his library). El Greco was no Baroque painter, but he was no mystic either.
What to do with an artist who slips through every explanation?
More here.