What's your idea of Paradise on earth?

Obscurity blinds us. Patiently we await enlightenment, but hope grows weary and the night of incomprehension affords no glimmer of dawn. Regular listeners to The Archers (R4) may be sharing my struggle with an intractable enigma. Yet, maddeningly, the villagers of Ambridge are not: one by one, they have glimpsed Eddie Grundy's guilty secret and responded appropriately. Goodness, they say, it's a long time since I saw one of those, or, it's going to be tricky getting it home, or Better not let Simon see that. And still nobody tells us why it's so unwieldy, what it looks like and why anyone, even Eddie, could possibly want one. Dear reader, can you help? What the blazes is a milking bail?

Over Ambridge, America and the Amazon the moon sails through the night sky like a Ship of Light (WS), bathing milking bails and threshing machines, rockets and ravines, pirates and pelicans in its cool, impartial pallor. Roger Fenby's superb, evocative compilation of lunar myths, poems and songs drew for inspiration on the mournful music of solo trombone or the plea of piercing strings; on the words of spacemen, shamans, philosophers, scientists and bards. Yet, whether chaste Greek goddess or rapacious Indian god; whether made of jade, cheese or granular glass, by some impenetrable magic the moon retains its ability to tantalise, fascinate and disturb.

So let us tackle lesser mysteries, like Paradise. There once was a family called Stein: there was Eisen and Ep, there was Ein. And they were all visiting Dr Schweitzer's leper colony in darkest Africa when Eva Braun came to call. Yes, this is David Pownall country, where the famous dead take holidays, and bump into each other and say silly things (which make me laugh). In A View From Genesis (R3) the four great men take their pretty, simpering guest to meet the cannibal King Give-A-Dam, whose conversion to Christianity is stalled in the Garden of Eden without a helpmeet. And lo, at last his Eve arrived and declared him to be sweet and kind, a lover of children, dogs and gardening. There was nothing left to be accomplished, save the Fall, brought about by the king's huge, risible serpent.

Noah Richler, who makes reliably excellent programmes, has also been In Paradise (R4) this week. The first of his series began dramatically in the rat- infested subway tunnels under New York, home to the otherwise homeless tramps New Yorkers call moles. One of them, Bernard, has planted two trees in that roaring, sooty underworld, and they strain upward through a single shaft of sunlight to the bright air above. Richler, too, advanced, heading towards the gardens of Iran, which some consider to be the geographical location of Eden.

On the way, judging by the discreet tinkling of bone china, he had tea with AS Byatt, who contributed little beyond expressing a grumpy desire for heaven to be an organic plot. But at last he reached the city of Yazd, known cynically as Tehrangeles, where rich men build their own heavenly gardens. Here, burbling streams defy the desert, watering thousands of cherry and almond trees in secret, walled gardens of delight.

Yet the Koran provides ambivalent instructions. Classically, a man lounges on flowers, being offered refreshing (non-alcoholic) drinks by beauteous dark-eyed houris, "as chaste as the sheltered eggs of ostriches". No place for an ordinary man, these days, when the finest plots are reserved for the young warrior-martyrs of Islam, and the Tehran fountains run red, like blood.

Even Woman's Hour (R4) ran a feature on the enclosed garden this week. It was a speedy romp through the growing habits of the centuries and, as so often, they seem to have got things most nearly right in the monastic houses of the Middle Ages, when monks spent their time growing medicinal herbs and nutritious vegetables.

When not gardening, they were in church singing the canonical offices. One of the chants most often used was the Salve Regina, the subject of this week's Kaleidoscope Feature (R4) (the Stabat Mater might have been a more appropriate Marian text, given the fact that Holy Week starts today). It was a mildly irritating programme to those of us whose convent childhood was frequently punctuated by the simple Gregorian chant. We waited in vain to hear it sung, and to hear the moving, beautiful English version, still widely used as a prayer. Instead, Richard Coles dwelt loftily on the less familiar solemn setting and on a clumsy new translation of the words.

It was interesting to learn of the power this ancient poem has held down the centuries, especially as described in a manuscript detailing 500 Marian miracles, recently rediscovered in the library of Sidney Sussex College. Still, to describe its current use as nostalgic aromatherapy identifies the basic lack of understanding that bedevilled the whole enterprise.

The same problem beset the inhabitants of Australia in 1929. Capricornia (R4) was a shocking play - horrifying, in fact, in its depiction of the casual, scornful cruelty offered by white settlers to anyone not conforming to their narrow view of racial respectability. An intricate plot led our hero from boyish, ambitious enthusiasm to the despairing realisation that a land of astonishing, untouched beauty had been ravaged beyond redemption by prejudice, greed and hypocrisy. Recorded in Western Australia, it rang true until the very last moment, when it descended into a really frightful corny ending that made me groan.

If you fancy neither Paradise nor Australia, you can always travel in the mind to Utopia and Other Destinations (R4). The trouble with this series is that Michael O'Donnell has given it more thought than his guests ever do, which seems idle of them, but then More's original Utopia - a sophisticated and organised society which really might work - has become synonymous with a vague, impossible dream. Ian McEwan and Victoria Glendinning, asked to imagine an ideal community, chose to ramble on about things they liked in no very coherent way. Both required cities for privacy and wilderness for escape but beyond that - well, they hadn't really worked it out. Glendinning did, however, know what bliss is. It lives within the ablative absolute. It is something having been done, she said - the dishwasher emptied, the shopping put away, the article finished. Ah, bliss.