Clouds was first performed in 423 BC at the City Dionysia festival, the chief religious and civic event of the Athenian calendar. Though he slaved over the composition and considered it his best work, Aristophanes suffered a humiliating third place, ousted by two arch-rivals. In Cratinus' lost Bottle, the alcoholic playwright left his faithful wife Lady Comedy to go on a drunken spree with Ms. Jugs. The Connus of Ameipsias, about which still less is known, also pilloried Socrates, dealing with his own musical education at the hands of the title character.

In retrospect it is likely that Clouds was simply too innovative for a rowdy festival audience accustomed -to a strict diet of dick and fart jokes – the staple of what is now termed Old Comedy. The primeval comic genre was a panto-style episodic vaudeville, which originated, according to Aristotle, with "the leaders of the comic processions" – a fertility rite involving scurrilous invective, obscene songs and 30-foot todgers. The roots were still evident in Aristophanes' day, when by convention every comic actor, regardless of his role, sported an oversized phallus. Aristophanes proudly claimed that this comedy was "chaste and pure ... the first to come on stage without stitching on a dangling red-headed bit of leather". Here the poet protests too much, for the play is rife with sexual and scatological humour – and not a few dick jokes.

Nevertheless, its innovations are still more evident, for Clouds is the first comedy which has what we might call a plot. It tells of Strepsiades, a rustic codger driven deeply in debt by his son Pheidippides' mania for chariot-racing with the lads. The old man has hit upon a way out: he needs to acquire the Wrong Argument, a spin-doctoring perversion of truth and justice taught – for a price – at Socrates' Thinkery. The unshod, bug-ridden pedants who haunt this institution have cast aside the traditional Olympian gods, worshipping the Clouds and other meteoric phenomena as they pursue the latest developments in science, philosophy and rhetoric. Yet these nebulous deities remain aloof from Socrates and his disciples, until with growing hostility they exact the vengeance of Zeus upon the Thinkery for its perversion of the natural order they represent.

Clouds thus ends with a rough justice alien to the festive spirit of Old Comedy, and this may have contributed to its failure. Indeed, the tone of the play – and of the choral passages in particular – is often closer to tragedy. We know from Euripidean melodrama that the two genres were beginning to converge at this time – as epitomized by the comic coinage "Euripidaristophanization". Interestingly enough, Plato's Symposium portrays Socrates and Aristophanes in drunken debate about whether the same playwright could compose both tragedy and comedy.

The friendly vignette discourages us from seeing the finale of Clouds as mere moralizing by the playwright. It is only by comic license that Socrates is made to stand for the troubling intellectual developments of the late fifth century: one easily imagines the great philosopher in the audience, joining in the laughter. To be sure, Socrates was notorious for his disheveled appearance, absent-mindedness and satyrish sexual appetites. But generally the Athenians seem to have felt a grudging fondness and admiration for the eccentric thinker. Despite his pedagogic association with Alcibiades and other revolutionary figures, his eventual execution on the charge of corrupting the youth and importing foreign gods was due as much to his own stubbornness and integrity as lack of concern and offers of help from his fellow citizens.

Like the best political cartoonists, Aristophanes excelled at presenting two sides of an issue in counterpoint – epitomized in this play by the debate between the Right and Wrong Arguments – to reveal the valid and ludicrous aspects of both. With its remarkable blend of low humour and weighty social content, the play remains difficult both to watch and perform. But the enduring relevance and strangely modern note of Clouds is more remarkable still. JCF