It's revenge of the plain woman, isn't it? A lifetime of bottled-up hurt from slights and insults and sniggers released in one glorious epiphany. “See!” the army of the ordinary cry. “It doesn't matter that we're not beautiful after all!”

Nothing else can explain the phenomenon of Susan Boyle, the humble, middle-aged churchgoer who, in the week since she appeared on the ITV show Britain's Got Talent, has metamorphosed into a global celebrity. In those seven days the YouTube clip of her singing has been viewed 20 million times. She has performed - on a live link from the living room of her council house in Scotland - for the millions more who watch Good Morning America, the top-rated US breakfast show. She has reduced the actress Demi Moore and an NBC presenter to tears, the latter on air. Hot invitations include one to appear on The Oprah Winfrey Show. As the Daily Mirror so tastefully summed it up: “Hairy angel is world sensation.”

Fairytales don't come any more satisfactory than this. The sisterhood of the plain, those of us who will never look like Girls Aloud, nor even Girls Aloud's grandmothers, are cheering as never before. Susan Boyle is the ugly duckling who didn't need to turn into a swan; she has fulfilled the dreams of millions who, downtrodden by the cruelty of a culture that judges them on their appearance, have settled for life without looking in the mirror.

This is a huge constituency, and it is weary of being disparaged. Women need an avenging force like Susan Boyle. No matter how brave, strong or resourceful they are, they get punished for not being glamorous; for being ordinary; careworn. At best they are treated as if they are invisible, at worst they are regarded as freaks. Which is what the TV audience did with Ms Boyle until she started to sing.

Last Tuesday, she told The Times that she hoped her story had resonance. “Modern society is too quick to judge people on their appearances. There is not much you can do about it; it is the way they think; it is the way they are. But maybe this could teach them a lesson, or set an example.”

And maybe it just will. Susan Boyle has electrified celebrity culture and inspired those far removed from it. She has highlighted, as never before, the gap between real people and the phoniness of the images that dominate our visual world. She teaches us how shallow our judgments are, how appearances matter not at all, how sex is not essential: how, contrary to what we are schooled to believe, the world does not have to belong to beautiful people.

In a way, she offers redemption for the sin of superficiality.

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