The ultimate driving force of William Penn’s adult life is inaccessible, as the Quaker phrase ‘Inner Light’ suggests. While a young man administering the family estates in Ireland, Penn experienced ‘convincement’, another Quaker term for what other Dissenters called conversion. But while these experiences were inward and personal, they had public consequences. Since they were potentially available to anyone, they brought in their wake a tendency towards egalitarianism, manifested in plain speaking, pacifism, and a refusal to swear oaths or doff one’s hat. These outward manifestations of private experience inevitably caused ructions in the hierarchical social structure of 17th-century England.

Ironically, Penn’s position in that hierarchy would have made him more liable to be doffed to than to doff. His father, Sir William Penn, was an admiral in the service of Charles II, and William junior would become a friend of King James II, though like other Quaker leaders he would find himself in and out of prison for his beliefs. Perhaps his privileged upbringing gave him the confidence to act as a spokesman and organiser for the Friends on both a national and international level. His access to the movers and shakers of his society enabled him to become proprietor of the Pennsylvania colony (named in honour of the admiral) and thus transform himself into one of America’s Founding Fathers.

Aware of the impossibility of exploring his subject’s innermost depths, Andrew Murphy focuses primarily on his contribution to a number of significant issues of his time, above all his advocacy of toleration and his evolving theories of government based on that principle. The austerity of this focus makes the occasional glimpse of domestic life all the more welcome. Penn wooed Hannah Callowhill (who would become his second wife) with three gallons of brandy (one for her mother, to whom he also sent a recipe for drying fruit). But some fellow Quakers wondered whether Hannah’s large dowry was really the attraction, given that Penn was perennially out of funds, despite owning vast estates in Ireland and America. Nevertheless, like his first marriage, this union would prove to be a loving one. Half a century previously, John Donne made a poetical address to his mistress: ‘O my America! My new-found-land!’ But Penn was able to make a similar comparison quite literally, claiming Hannah’s love was ‘a proprietorship [I value] above that of Pennsylvania’.

Murphy makes clear that Penn was complex to the point of contradictoriness. He was fabulously rich by most standards yet never had any money; he was of high social status but embraced a religion of equals (well, more or less: he kept slaves); he was one of the pioneers of representative government but a valued adviser to a king; he was deeply spiritual but preoccupied with material affairs. He seems to have been unembarrassed by these dichotomies. ‘I desire to extend religious freedom,’ he wrote, ‘yet I want some recompense for my trouble’ — a mixture of motives he shared with other American pioneers, and one which informs the politics of the United States to this day. He was celebrated for his humane treatment of Native Americans — referring to the way that they were treated in other colonies, he tersely claimed ‘I am not such a man’ — but nevertheless began selling their land before he’d paid for it, and in due course his heirs swindled the Lenape Indians out of a million acres of territory in the notorious Walking Purchase of 1737.

Murphy is clear-eyed about Penn’s faults and weaknesses — he was ‘well-practised at self-pity’ — but he is more concerned to plot the intricacy of his course through a many-faceted life than to sit in judgment upon it. Though the book opens with Penn in later life confined, Micawber-like, in (or at least near) the Fleet for debt, this is not a novelistic biography that sets scenes, features rounded characters and evokes atmosphere. It’s probably fair to say the book is not really aimed at the general reader. It doesn’t attempt to convey the nature of Quaker worship but concentrates on the Friends’ disputes between themselves and with society at large. Similarly, while we are given Penn’s account of the abundant produce of his colony  — ‘sassafras, cypress, cedar, black walnut, diverse wild fruits, copper and iron’ (he was ever the salesman) — we aren’t encouraged to visualise the world of colonial Pennsylvania, or of colonised Ireland for that matter.

Instead of that sort of local colour, Murphy gives us a meticulously researched account of the nuances of Penn’s dealings with the varied issues and groups he confronted during his extraordinary life, providing an invaluable resource for anyone with a serious interest in the history of Quakerism, the development of governmental theory, or the vexed politics of Penn’s ‘holy experiment’.