An exhibition of paintings by a 17th-century woman depicts subjects often routine to the point of banality. But, argues Richard D North, they show that the divine can be found in the most humdrum and even painful subjects

A trussed lamb makes an odd devotional image. There it lies, feet bound, caught in indignity and perhaps pain. It wears a look - if a young sheep's look can be interpreted accurately - of mute appeal. At best, it is a baleful look. If this were the 20th century, such an image would most likely be seen, grainily photographed, in a newspaper advertisement for the Royal Society for the Protection of Animals. It is, in a way, more shocking than anything essayed by Damien Hirst. This is a living creature portrayed not as a carcass on its way to be meat, but as the living embodiment of joyful spring on its way to slaughter.

Josefa of bidos, rare in being a woman painter in early 17th century Portugal, was portraying an Agnus Dei - the Lamb of God - and the creature, perhaps two or three months old, is hog-tied, ready for the knife on its stone slab, an altar with no cloth in sight.

The peculiarity of the thing is not merely that we are startled to see an animal's suffering transformed into an object of religious devotion, but that anything quite so commonplace could be thought likely to reward long reflection. So it is quite right that the show of Josefa's paintings, recently seen in Washington and now at the European Academy and the Accademia Italiana, is called "The Sacred and the Profane". The best of the paintings are still lifes, a kind of work which was quite new then. Its subjects were often routine to the point of banality. But the most humdrum of the scenes is capable of producing something like awe.

Josefa's work was part of a growing trend. Gabriele Finaldi, the curator of late Italian and Spanish painting at the National Gallery and of the 1995 "Spanish Still Life" show there, says, "Still life painting happened all over Europe from the end of the 16th century. Perhaps it arises partly because the technical accomplishment is in place: people could paint light falling through glass, and so on. And then, people were reading in Pliny about classical still life paintings which we no longer have. People in the 17th century were interested in illusion: they were interested in the idea of paintings of grapes which fooled birds into pecking the picture, as they had read about in the classics."

But there is something in the religious and intellectual temper of the time, too, which could use the new still-life style. According to Finaldi: "These developments go with advances in the worlds of science and observation. Catholic countries had rather done down the senses as negative and dirty - and were perhaps rethinking that." A still life of an object, however familiar, lets the viewer consider more deeply the metaphysical meanings that lurk behind the tangible world.

For Spanish and Portuguese, more even than anywhere else in Europe, metaphysics came drenched in religion. Josefa, at least in youth, was a sort of part- time nun. As a painter living in a small provincial city in a country which itself was provincial compared with Spain, she was heavily derivative of more accomplished Spanish painters. The trussed lamb is an example: the far more celebrated Francisco de Zurbarn painted several 20or 30 years earlier. She depended on commissions from religious and monastic orders, and thus worked within strict and pious conventions. While she often worked from engravings of better painters, she was also very Portuguese and original in the almost peasant cheerfulness which usually eluded the masters of the austere, sunbaked plateaux to her country's east.

She puts homely details into her versions of famous images of the holy family. And when she comes to do still lifes of bigger collections of food, fruit and flowers, she showers the whole scene in petals, berries, and twigs, with a fine and joyous disregard of perspective or order.

Angela Delaforce, the curator of Josefa's show, had a Portuguese childhood herself, and remembers eating in a house whose table was supplied with cakes from a local convent. "The nuns were famous for making these cakes and sweet things," she says. Josefa paints them very often and not so much well as with infectious excitement. It's tempting to see them as something like blessed bread. Dr Delaforce doesn't approve of reading too much into the paintings. The 17th century mind adored symbolism and hidden messages, which has provided American academics especially with the excuse to read a narrative into every petal and crumb of still lifes or any other old painting. In one famous case, a bunch of parsnips became, in one critic's imagination at least, the nails of Christ's crucifixion. "I'm not the kind of art historian who likes to read in painting more than the evidence will allow," says Dr Delaforce. She stresses that objects in still lifes do "acquire a sort of mystery" because of the way w e concentrate on these illusions of reality.

Whether the nuns thought much more of the cakes than that they were a source of revenue, or Josefa painted them because they were spiritually as well as actually appetising, cakes made in convents certainly did figure at Christmas and Easter tables. A religious mind would have noted that the bible is stuffed with references to food of every sort. The snail and the butterfly which figure in one of Josefa's paintings may indeed be there as symbols of humility and transcendence, as the American catalogue for the show has it.

The rest of Josefa's still lifes may or may not have been devotional, but her Agnus Dei very probably was. The lamb powerfully speaks of sacrifice. It links the followers of the New Testament with the older beliefs of Judaism and beyond that with pre-historic practices. Abraham trussed his son Isaac and laid him on a makeshift altar before God accepted that his faith had been tested thoroughly. It was to Moses the shepherd that God outlined how the Passover sacrifice of lambs should be undertaken. Christ as a youngster is foretold as "the lamb of God which beareth away the sins of the world". Josefa's customers, less squeamish and more pious than anyone today, also lived far tougher physical lives than most of us now. What would the brief and probably slight suffering of the lamb matter if it served so grand a purpose as to further the work of the church in saving souls?

The show runs until 16 November at the European Academy and Accademia Italiana, 8 Grosvenor Place, London SW1X 7SH (0171-235 0303). pounds 3, pounds 2 concessions. Dr Gabriele Finaldi, is talking about Josefa de bidos and her influences on 12 November at the European Academy and Accademia Italiana: `God among the pots and pans', 6.30pm. pounds 10, pounds 8 concessions