The philosopher Bertrand Russell tells in his autobiography how as a child he was given a Bible by his grandmother, inscribed with a verse from Exodus 23:2: ‘Thou shalt not follow a multitude to do evil.’ A natural individualist and strongly independent thinker, Russell will not have needed reminding of that principle as much as might those with less fierce intelligence than his. He was also keenly aware that, for the vast majority of people, ‘following a multitude’ is often a comfortable option and one that can seem entirely consonant with one’s individual viewpoint. Living through eras in which both murderous Communism and brutal Nazism caused the death and suffering of tens of millions, he was in a position to see how something akin to mass hysteria could operate on different levels, blinding individuals to the crimes done in the name of ideology, just as no lesser horrors had, over the centuries, been perpetrated in the name of religion.

Perhaps the earliest portrayal of mass hysteria – in this case in the cause of religious worship – is to be found in the fifth-century BC Greek drama the Bacchae by the Athenian tragedian Euripides. The bacchants, or maenads, were inspired female devotees of the god Bacchus, or Dionysus. The play portrays the establishment of the god’s cult in the city of Thebes, with its terrible consequ­ences for the city’s ruler Pentheus and his family at the hands of women driven from their homes by divine frenzy and now living on the slopes of Mount Cithaeron. In the oblivion engendered by their religious ecstasy, they are driven to gleefully tear Pentheus apart with their bare hands; and the woman who takes the lead in that frightful killing is none other than Pentheus’s mother, Agave.

Part of the power of the play lies in the ambivalence the Athenian audience is bound to feel about Dionysus, given the horrendous act commit­ted by the women at the god’s behest. As the play makes evident, however, the audience will have been expected to celebrate and continue the worship of Dionysus, recognising the god as simultaneously the provider of blessings (such as wine and ritual release) and of dangers (such as the consequences of drunkenness and loss of self-control). In his classic commentary on the Bacchae (1960), the Oxford Hellenist E. R. Dodds writes: ‘To resist Dionysus is to repress the elemental in one’s own nature; the punishment is the sudden complete collapse of the inward dykes when the elemental breaks through perforce and civilisation vanishes.’

Ancient Greek women had no political power. The play therefore presents an unusual scenario – purely imaginative in fact, though for centuries scholars and readers were inclined to take it as historical – in which the female devotees of Dionysus are able, with the god’s help, to assert their power by taking control from a repressive ruler. He in turn has sought to ban the worship of Dionysus and to reassert order in the city. While there can be no doubt as to who will ultimately be the winner in this conflict, the victory of the god comes at a terrible cost to the human victims of his wrath. It is no comfort to Agave to discover, when she is eventually shaken out of her blind religious frenzy, that the object she is victoriously brandishing, thinking it to be her god’s adversary, is none other than her son’s severed head.

Dodds was inclined to compare the actions of the bacchants to historical outbreaks of mass delirium that have been recorded over the centuries. One such episode was dramatised in a novelistic treatment by Aldous Huxley, The Devils of Loudun (1952). Huxley based the story on a historical event that took place in 1634, when a group of nuns in the French town of Loudun claimed to be in the possession of demons. After the matter was investigated by the Church author­ities, a local priest was accused of communing with evil spirits; he was convicted of sorcery and burned at the stake. More widely familiar is the story of the Witches of Salem, which in 1692-3 saw more than 200 people in Salem, Massach­usetts, accused of witchcraft. Around 20 innocent people were put to death before the mass hysteria of the young women accusers, supported by cruel and over-credulous male judges, was acknowledged as such.

These curious and tragic episodes demonstrate how crowds can become infected by a kind of hysterical frenzy that blinds them to rational argument and isolates them from normal social mechanisms (though there is always the possibility that they can be manipulated by malign actors as well). The notion that women, as repre­s­enting such a group, might band together to challenge male authority, is a theme in late fifth-century comedy no less than tragedy: Aristophanes’ Lysistrata of 411 BC  comically dramat­ises the fantasy scenario of Greek women at the time of the Peloponnesian War (431-404 BC), who agree to deprive their husbands of sex in order to force them to negotiate peace. Driven to desperation by enforced abstinence, the warring sides agree to be reconciled – a resolution that was, sadly, not matched by historical events.

The idea of a disadvantaged group – or at least one so self-identified –succumbing to symptoms of mass zeal in the name of a cause has points of comparison to the actions of young people on university campuses today. A recent discussion with some of the students recorded on video shows an interviewer asking ‘Why are you demonstrating?’ The answer is ‘To support the cause’. When he presses ‘What is the cause?’, they respond ‘We’re not here to answer questions, you must ask the organiser.’ Today’s demonstrators wear keffiyehs and brandish posters to identify their cause; in the Bacchae the chorus of maenads wear fawnskins and brandish ivy rods to identify themselves as worshippers of Dionysus. The maenads dance and chant (lines 73-6) ‘Blessed are they who, being fortunate and knowing the rituals of the gods, keep their lives pure and their souls initiated into the Bacchic revels, dancing in inspired frenzy over the mountains with holy purifications.’ Dodds comments on the ‘inward feeling of unity of the thiasos [crowd of worshippers] and through it with the god: such merging of individual consciousness in group consciousness is the attraction and the danger of all religion of the Dionysiac type’.

The Bacchae can offer insight into the sense of belonging that following a ‘multitude’ in support of a cause engenders. It also warns of the tragedies that such episodes can precip­itate, and of the perils that so often accompany their resolution.