Francis Bacon (British, 1909–1992) Head VI, 1949 Oil on canvas; 36 11/16 × 30 1/8 in. (93.2 × 76.5 cm) Arts Council Collection, Southbank Centre, London © 2009 The Estate of Francis Bacon / ARS, New York / DACS, London

Broadly speaking, the Irish-born painter Francis Bacon was an expressionist, although that hardly begins to describe his often violent and always difficult paintings. The subject of a large exhibition at the Met (running through August 16), Bacon, who died in 1992, lived an anguished life. Looking at his paintings evokes pain and even fear — probably not nearly the pain and fear he himself experienced as an artist — and some people literally can’t look at them.

Years ago, for example, I was with my sister, who had always struggled with mental illness. We were spending the afternoon doing the galleries in New York and strolled into a show of Bacon’s work at the Marlborough Gallery. She took one look at the paintings and said, “I can’t take this. I’ll wait outside.” (She stepped outside and immediately lit a cigarette.) I’d be the first one to admit that you don’t have to have mental-illness problems to empathize with my sister’s reaction.

With 65 paintings concentrating on his work from the 40s through the 60s, as well as a true-to-life photograph of the artist’s famously messy London studio, this exhibition is the perfect opportunity for an artist like me — who’s spirit is by nature the very opposite of Bacon’s — to ponder his work. Artists and critics I know are evenly split on their opinion of him. There are those who think he’s dreadful — hardly a painter at all, merely an illustrator using designy colors and an affected line. Then there are those for whom he’s one of the greats.

I don’t know about great, but to me, Bacon — taken in a small dose (the Met exhibition is a huge dose, probably too huge) — is a healthy antidote to the bourgeois insistence (which I, for one, appreciate no end) to plaster a cheerful veneer across existence itself. It’s understandable. We need our illusions in order to avoid dwelling on the thought that lurking inside each of us is nothing but gurgling, roiling, rotting mucky stuff.

Bacon’s paintings — most of which are portraits of one kind or another — reflect the way this man always drifted over to this terrible fact. For him, forgetting was impossible. His is a dark and existential vision, the painterly equivalent of the saddest and most despair-filled lines of poetry in T.S. Eliot. His famous “screaming pope” paintings (which had been the cause of my sister having to leave the gallery) are violent riffs on Velásquez’s famous portrait of Pope Innocent X. Bacon strips the pope of the authoritative, commanding and deeply wary personality revealed by Velásquez to expose instead a terrified and terrifying monster.

Bacon’s other pictures — of mad spinning dogs, silently screaming baboons, and alienated, open-mouthed businessmen alone in hotel rooms — are equally terrifying. For Bacon, the mouth, in particular — whether part of an animal or a man — is a riveting orifice. It’s ugly. He likes to portray it wide open, or screaming, or collapsing, or mangled. Bodies and faces are horrible as well, torn into pieces and then mangled into bloody blobs that can resemble hunks of meat. His art is often homoerotic, but not always. Sometimes it’s merely the stuff of misery. Always it’s dark, sad and lonesome.

So why subject yourself to this stuff, you might ask? Well, first off, don’t if you don’t want to. (This should hardly be necessary to say, but when artists are honored at a place like the Met, visitors often think they’re “supposed” to like them.) Some people want their art to always come up sweet, and for those I can only say look out — there’s a lot of art that doesn’t do that. Second, if you suffer from chronic depression or mental illness of any kind, definitely don’t look at Bacon. Art is always potentially disrupting, since it stirs up repressed desires that would otherwise remain dormant.

Bacon is hardly the only artist who’s full of horror. Picasso’s Desmoiselles d’Avignon, Goya’s series on the disasters of war, Grünewald’s Isenheim altar — all are terrible, horrifying images. Bacon’s are no worse. If you want a dose of the bleak to keep you honest, this show is for you.