When you write a story, you make a commitment as surely as if you adopted a political position or declared your love for another. The writer lays himself or herself open to rejection. The audience may find his story ridiculous or boring, and its moral or absence of morals repulsive. They may refuse to make their reciprocal commitment and stick with the story to the end. For the writers of mysteries in particular, not keeping readers is the keenest of failures. The final pages deliver the solution, and a reader who cannot get there will never read their books again. Holmes and Watson are characters who have entered the world's imagination. But if Conan Doyle had not been able to conclude his mysteries with explanations that made everything that had gone before comprehensible, no-one would have remembered them.

Sherlock avoids all the commitments of a storyteller, and spares the audience from making their commitments too. Moffat and Gatiss are like stand-up comics. If you don't like this story, they seem to say, we've got another one coming. The thin, barely coherent plots may not please, our characterisation may be perfunctory, but we can offer you irony, strained family relationships, friends falling out of friendship and back in again, jokes, romances, knowing references, new technology, banter, special effects and graphics overlaying the film.

The script's recognition of the show's fans who obsess about the series on Sherlock's websites is suggestive. Sherlock may dispirit anyone who loves storytelling but for the generation brought up on the web, its neurotic flickering between subjects and emotions is the closest television drama has come to mimicking the internet. You do not have to go all the way with the American writer Nicholas Carr — "Google is making us stupid" — to realise the web boosts the fickleness that television remote controls first encouraged when they arrived en masse in the 1980s. You rarely lose yourself in a single consuming experience on the web as you can in a well-written book or drama. You bounce from Twitter to YouTube, to an article a friend has linked to on Facebook. You read the first three paragraphs, grow bored and your wandering eyes see a link to a film trailer. You watch it for 90 seconds, and think about buying a ticket online. But before you find the resolve to commit to hours in a cinema, you decide that you must go back to Twitter to see if anyone has followed you or retweeted your last joke or linked to something interesting or funny in the ten minutes you have been away. You jump from fiction to news to acquaintances, never staying long enough to stick with a story until the end, or understand what lies behind a headline or build an acquaintance into a friendship. No wonder Sherlock is so popular. It fits our time perfectly.

The web is now the main medium of entertainment in the developed world. Television is dependent on it. Its future lies on web iplayers, and probably in commitment-phobic, jittery dramas like Sherlock.

I do not want to put on a portentous voice and predict the death of television drama. Like the "death of the novel" or the "death of newspapers", it will never happen. But stories in the Sherlock mould will be all around us, filling the screen with bright random patterns and then vanishing.