With a newly skeptical eye, I walk among the three galleries that hold the Black Paintings and find myself drawn less to the grotesque ''Saturn'' than to the disconsolate ''Dog,'' which gazes like a character in a Beckett play toward a vast emptiness to the right. ''The Dog,'' like several other Black Paintings, is a classic of modern art. ''There is not a single contemporary painter in the world that does not pray in front of 'The Dog,''' Manuela Mena observes. As I stand before it, I think of a story she recounted. The painter Joan Miro, in the last year of his life, paid a final visit to the Prado, and Mena was assigned to escort him through the museum. When she asked him what he would like to see, he said, ''I want to see 'The Dog' of Goya.'' He sat in front of it for half an hour. Then she asked if he wanted to look at anything else, and he had her take him to ''Las Meninas'' of Velazquez, which is perhaps the most revered painting in the world. ''For him, 'The Dog' and 'Las Meninas' were of the same level intensity,'' Mena said. She looked at me challengingly. ''We cannot send 'The Dog' to the museum basement because it was on the apparently nonexisting second floor of the Quinta.''
. . . Arthur Lubow, contributing writer for The New York Times Magazine.