Towards the Light, By A.C Grayling

A philosopher traces the gradual defeat of bigotry by the forces of rationalism

This is an easy book to agree with, and to admire, but a difficult one to enjoy. A C Grayling covers a huge historical and geographical span, he has done an impressive amount of reading, and he tells some fascinating stories. But there is something deadening about his prose, especially when he is writing about ideas rather than events.

Subtitled "The story of the struggles for liberty and rights that made the modern West", the book is, as Grayling says, "a work tracing the application of an idea in history", that idea being individual liberty. The title alone is enough to alert you to the fact that what he is writing is Whig history, in which individual events are subsumed to the march of progress; he admits as much himself on his opening page. Only in our own day is progress seen to stall, as individual freedoms are made to take second place to collective security.

He does not define his key term, "liberty", until his closing pages. He chooses instead to allow "the concept to evolve with the narrative of its history, as it did in fact". It is quite a narrative, stretching from classical antiquity to the identity card debate. Underlying it all is a long-distance dispute with Lord Acton, the 19th-century Catholic historian, who saw liberty as a gift of Christianity.

Grayling is having none of that. He begins with an account of how, after a brief period of tolerance, medieval Christianity set about rooting out heresy. In Spain, Torquemada and his Inquisition tortured and murdered thousands of Jews, Muslims and Christians. After Martin Luther had opened the door to discussion of the fundamentals of faith, Ulrich Zwingli and John Calvin slammed it shut, ruthlessly crushing opposition.

Calvin enthusiastically supported the death penalty for heretics. "This law might at first appear too severe," he wrote, commenting on a passage in Deuteronomy demanding the stoning of false prophets. "Why should anyone be punished thus for merely having spoken? But if anyone slanders a mortal man he is punished; shall we allow a blasphemer of the living God to go unpunished?" It is a comment with obvious resonances in our own time, although this time Christianity is not guilty.

Grayling tells a story of heroes and villains. One hero was Sebastian Castellio, a protestant who fell foul of John Calvin after defending Michael Servetus, a Spaniard who had been burnt for denying the trinity. Castellio embraced freedom of conscience in a very modern way. People should apply reason to the complexities in scripture, he said: "Reason, I say, is a sort of eternal Word of God."

Another unsung hero is Anthony Benezet, a Quaker who began campaigning against slavery as early as the 1750s, when his church was still in favour. Other heroes of the struggle are more predictable: Luther, at least at the beginning; Milton; John Locke; Montesquieu; Robert Owen; Mary Wollstonecraft; and countless anonymous authors of demands, charters and statements of rights.

Then there are the villains: it is no surprise to find most of them wearing either clerical garb or a crown. After the Reformation, Grayling sees the Glorious Revolution as the key event, leading to the end of the Divine Right of Kings, not only in Britain but elsewhere. It was a direct inspiration to the Enlightenment intellectuals in France.

It is in the 18th century, battling domineering religions and absolute monarchs, that Grayling is most at home: certainly this is the era to which he devotes the most space. He seems less engaged the further he goes from there. A single chapter, called "Slaves, Workers, Women and the Struggle for Liberty", marches determinedly through everything from the Reform Acts and Chartism to the struggle against slavery and female emancipation. The latter is despatched in 12 pages. There is a reference to Rosa Parks on the jacket and a picture of Martin Luther King in the slightly random selection of photographs in the centre of the book, but he mentions neither; perhaps King's Christianity did not fit his thesis.

This is not a book that works steadily through a topic. Instead, chronological and thematic approaches tend to clash; you think he's finished with a character or a subject and moved on, only for him to circle back on himself. He is also slightly lax about the way he introduces subjects, for instance spending four pages talking about the Federalist Papers before reminding us what they were. In general, a high level of knowledge is assumed. "When Priscillian was put to death in 385," he tells us, "many Church notables – among them no fewer than three saints: Ambrose, Leo and Martin of Tours – condemned the Spanish bishops for ordering Priscillian's execution." Yes, but who was Priscillian?

Much of this can be put down to a lack of editing. There are some very long sentences here, piling subclause upon clause; they might have been pruned. Most of the really pungent writing belongs to the people Grayling quotes: Luther, Diderot, Voltaire, Burke, but also the Levellers, the Chartists, and the hungry farm labourers of 19th-century Sussex. Grayling does, however, conjure up some ringing phrases in his final chapter, which reminds us of our duty to defend our civil liberties: "It is what we owe the dead who bought them for us with their lives, it is what we owe ourselves in our aspiration for good lives, and it is what we owe those whose lives are to come: the inestimable gift of liberty, and the security of inalienable rights." *

Bloomsbury, £20