It is a solution that many jaded by the dating game might consider attractive.

Thomas Day was a wealthy young man disappointed by the women he encountered in mid-18th-century Britain, especially those who had spurned his not infrequent offers of marriage. So he decided to create a spouse.

Using his money and social status, he took advantage of one of the more progressive institutions of Georgian England, the foundling hospital, to procure himself two 12-year-old orphans. Although neither knew it, his intention was that the better candidate would eventually become his wife.

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But Day, with his dishevelled, long hair, scruffy dress and predilection for bathing in country streams, was not seeking a bland example of fickle femininity. Indeed, his expectations surpassed those of the most discerning internet daters. He wanted a partner with whom to have the discussions on politics and literature he enjoyed with his male friends, an unusual requirement in an age where women were not expected to have the intellectual qualities of men.

She should also be robust and able to share his austere lifestyle: strong, plump arms were essential. But, crucially, she would be pure and virginal – and utterly subservient to his demands.

The challenges and pitfalls involved in creating the perfect woman have been detailed by many. from Ovid to George Bernard Shaw (while the perfect man has escaped widespread literary interest).

But Day thought he had a ready-made guide in the form of the treatise, Emile, a challenge to child-rearing orthodoxy from the unlikely hand of philosopher and educationist Jean-Jacques Rousseau in 1762.

He challenged the religious doctrine that children are born with original sin. But he also disputed the idea that they are a wax to be moulded at a parent's whim. For Rousseau, children were born good then corrupted by civilisation. He therefore set out a system of education based at least initially on children's interactions with the natural world.

While Rousseau would deny that he intended his work to be a practical guide, it prompted well-to-do parents to douse their children in ice baths and expose them outdoors to learn to fare for themselves. This would be Day's template for the education of the two charges he named Sabrina and Lucretia.

Wendy Moore provides a mesmerising account of Day's experiment, the demanding schooling and physical challenges endured by the girls, from having wax melted on the skin to withstanding the shock of having a shotgun fired at close quarters.

As well as the telling little details, such as the tokens left with their infants by departing mothers at the door of the foundling hospital, Moore highlights big issues of 18th-century historical study as well as our time. What it meant to be a man, or woman, chivalric values, the impact of social status and attitudes to mental illness, are all addressed.

But these are handled with a light touch because Moore has such a captivating story to tell, which she conveys with the pace and ingenuity of a novelist. Her skill lies part in her tenacious tracking down of sources – she discovered the link between the girls, the foundlings and the hospital where their mothers first deposited them. But this never gets in the way of bringing life to the women involved.

In particular, Sabrina, who lasts the longest under Day's tutelage, becomes a convincing personality under Moore's pen, someone who can show utter devotion to the companion and protector yet reacts with horror when his intentions are discovered.

And, despite the trials she faces, she is someone who, through her own efforts, builds a life for herself and her children.

Moore avoids treating the women primarily as victims and in so doing challenges one-dimensional accounts of the position of women in Georgian society.

Comparisons with the relative liberation of our time or a previous Golden Age overlook the evidence that, while power was undoubtedly weighted towards men, women were not completely powerless. Sabrina, no matter how precarious her social position, resists being told who to marry. Likewise, parents told by Rousseau to give their girls the most banal and regressive of educations to prepare them for domesticity, instead sent them out into the woods to forage with their brothers.

Men and women may have been drifting towards separate spheres but in Georgian Britain these overlapped messily.

Day, perhaps because of the fundamentalism of his outlook, is the character hardest to understand. He showed egotism and cruelty yet his relentless search for the best way to live with little heed of the prevailing orthodoxies was admirable. How could a man so willing to defy the orthodoxy of his times, someone attached to animal rights, author of a powerful poetic polemic against slavery and an extraordinarily generous philanthropist, behave in such inhumane ways?

Nevertheless, what in less skilled hands could have been another misery biography is a paean to the obstinacy of the human spirit