In 1791, a tall, good-looking ex-naval officer called Richard Brothers claimed to hear the voice of an angel predicting God’s imminent destruction of London. In the same year, William Bryan – a Bristolian with mellifluous voice and “clear and gentle” eyes – prophesied the overturn of global monarchies, followed a few years later by the “fall” of Bristol, and an earthquake in which London would “burn like an oven”. Their critics accused Brothers and Bryan of “enthusiasm”, of falsely believing they were acting under divine inspiration. Satirists aligned them with the bloodiest of French revolutionaries. They seemed to exhibit the same disrespect for established social hierarchies, the same untamed emotions, the same wild eyes, torn clothes and dangerously unkempt appearance.

Judging by the criticism levelled at Greta Thunberg – the 16-year-old Swedish climate activist who launched a Skolstrejk för klimatet (School strike for the climate) in August 2018 – many fear her as the Brothers or Bryan of our times. She has been accused of alarmism and fearmongering, with a “doomsday” prophecy of climate catastrophe, necessitating changes that will crash the global economy. Jeremy Corbyn’s brother Piers Corbyn has dismissed Thunberg as a “brainwashed child”, an inspired puppet of cynical adults. Spiked magazine’s Ella Whelan sees Thunberg’s school strike as an encapsulation of her entire method: a rejection of rationalism and education for “kneejerk, panicky responses” and wild, self-indulgent emotion. Thunberg is painfully aware that “people tell me that I’m retarded, a bitch and a terrorist, and many other things”.

But her speeches – now collected and published under the title of her refrain, “no one is too small to make a difference” – give the lie to these caricatures. Yes, she reiterates, “I want you to panic … I want you to act as if our house is on fire. Because it is.” But this is offset by dispassionate emphasis on bullet-pointed facts and figures, and the defence that emotion – even panic – is completely rational.

Perhaps Thunberg is a prophet after all. Brothers and Bryan leaped to fame in the 1790s, when their visions of toppling hierarchies and ravaged cities gave shape to people’s inchoate hopes and fears about change and corruption after the French Revolution. Their prophecies confirmed the widespread sense that to live in 1790s Britain was to live in a time of profound, unsettling and not necessarily optimistic change.

Thunberg speaks to a people acutely aware of living in a time of transition, on a knife-edge between possible futures

Thunberg’s appeal to us now is slightly different. Her simple emotion and “black-and-white” rationalism suggest authenticity and trust to her audience, many of whom are wary of adult experts suspected of harbouring hidden agendas.

But most of all, whereas Brothers and Bryan’s prophecies gave shape to public fears of catastrophe and collapse, Thunberg speaks to a people acutely aware of living in a time of transition, on a knife-edge between multiple possible futures. Her argument is not driven by a belief that we are all doomed, but is cut through with tentative hope. And as a small, isolated figure, with her pigtails and open face, poised bravely behind an enormous lectern, facing down a roomful of powerful, suited adults, she embodies what it’s like to be an individual who yearns for change, against a juggernaut of commercial and political interests defending the status quo. I wonder if many of us right now, across a multitude of political persuasions, see ourselves in Thunberg, in the fragility of our political and environmental hopes, and our sense of personal impotence. As she says: “I’m too young to do this. We children shouldn’t have to do this.” A greater readiness to involve ourselves in collective action would go a long way towards lessening not just Thunberg’s vulnerability, but our own.

• No One Is Too Small to Make a Difference by Greta Thunberg is published by Penguin (£2.99). To order a copy go to guardianbookshop.com. Free UK p&p on all online orders over £15.