Niall Ferguson has had an epiphany. But as is often the case, it is not entirely easy for others to know just what this vision involves. His one-sentence summary is simple enough, but his elucidation and elaboration of it are not. The simple premise is that much of history is best understood as a contest between networks and hierarchies. The image of the square and the tower makes the point: hierarchies embody ‘vertical’ order and top-down control, while networks are based on ‘horizontal’ connections – ties of many kinds but not between order-givers and order-takers. Networks are the sphere, says Ferguson, of influence but not straightforwardly of power.

The central thesis of the book is that ‘social networks have always been much more important in history than most historians, fixated as they have been on hierarchical organizations such as states, have allowed’. He thinks that there have been two historical periods when networks have been especially important. The first is the era of Gutenberg, the period following the introduction of the printing press to Europe. The second is our own time, beginning roughly in 1970. Between these two ‘networked eras’, hierarchies ruled, from around 1790 to 1970. The high point of the hierarchical imposition of order was the mid-20th century, ‘the era of totalitarian regimes and total war’.

Unsurprisingly, then, the chapter entitled ‘When Gutenberg Met Luther’ forms a sort of hinge in Ferguson’s account. Having disposed of hierarchy in a short discussion of the fall of the Roman Empire in contrast with the persistence of the Chinese Empire, Ferguson moves rapidly through the early Renaissance, with its networks of merchants and subsequently bankers, to what he regards as the great transformative force. Johannes Gutenberg created his press at Mainz sometime between 1446 and 1450; the technology spread rapidly throughout Germany and was very soon adopted in Switzerland, Italy and Spain.

‘Without Gutenberg,’ says Ferguson, ‘Luther might well have become just another heretic whom the Church burned at the stake, like Jan Hus.’ This surely underestimates the importance of the fact that Luther had a princely protector, Frederick III, Elector of Saxony. The German princes had their own grievances with the Catholic Church; it was not Henry VIII alone who resented the Church’s taxation of subjects from whom their rulers wished to raise funds for their own purposes, not the building of St Peter’s or whatever other projects the papacy had in mind.

What is certainly true, however, is that Gutenberg’s technology permitted the spreading of Luther’s views far and wide throughout the German-speaking world. The painstaking efforts of copyists toiling to produce single copies of service sheets, let alone books, had instantly become obsolete; during the 16th century, almost five thousand editions of Luther’s works were printed, to which we should add some three thousand editions of the Luther Bible. It wasn’t just the sheer quantity that made a difference; the fact that his writings were overwhelmingly in German made them accessible to the laity as they would never have been in Latin.

‘Was the Reformation a disaster?’ asks Ferguson. Between 1524 and 1648 central Europe was racked by sectarian and confessional conflict; on some estimates the Thirty Years’ War killed around 30 per cent of the German population. Britain did not escape upheaval, either. Mary Tudor’s failed attempt to restore Catholicism was followed by her sister’s unflinchingly coercive imposition of the Anglican compromise between Puritanism and Catholicism. In the next century, the English Civil War killed perhaps 100,000 people in England and Wales, and proportionally more in Scotland and above all Ireland. It is, Ferguson observes, easy to think that the doctrine of the ‘priesthood of all believers’ led in short order to bloody anarchy, and that the traditional, hierarchical order of monarchy and papacy was essential to peace. On the other hand, Protestantism seemed to liberate intellectual and economic forces that in due course produced both political and industrial revolution.

The bulk of The Square and the Tower consists of some sixty short essays, organised chronologically and taking us from the decay of the Roman Empire all the way to the rise of ISIS. Some readers will worry that Ferguson does little to explain why he has selected the topics he chooses to discuss. Brief essays on such events as Paul Revere’s ride don’t obviously advance the thesis that history has been driven by conflicts between the principle of hierarchy and the reality of networks. Others, however, will be grateful for Ferguson’s lightness of touch and vividness of expression, which make a substantial book less difficult to read than its bulk might suggest.

At all events, there is much to engage the reader. Ferguson is particularly engrossed by the implications for the international order of the contrast he sees between networks and hierarchies. After the excesses and disorder of the French Revolution, there was a period that might be described as ‘empires fight back’, or the restoration of hierarchical order. The first significant figure in this movement was, of course, Napoleon, whose career can be portrayed as one that brought order to France and disorder to Europe. But Ferguson is also interested in the restoration of order after 1815 and its remarkable persistence until 1914. This was the subject that his hero Henry Kissinger took for his doctoral research topic as a Harvard student, and it is one that engages him still in his nineties.

In Ferguson’s analysis, what emerged after the Congress of Vienna was a ‘pentarchy’, a system in which the great powers dictated the international politics of Europe in such a way that major wars never broke out. The four Continental powers – France, Austria, Prussia and Russia – preserved a balance of power, with occasional British interventions. ‘There were, in effect, world wars in the eighteenth century as there were in the twentieth – the Seven Years’ War was a truly global conflict – but there was no world war in the nineteenth century.’

Is there anything comparable today? In spite of the proliferation of international organisations of all sorts, Ferguson follows Kissinger in thinking we live in a time of disorder. Global conflagration is at least a possible outcome of the present instability, and we already live in a world in which terrorism has the upper hand and mass migration undermines social order in the liberal democracies. The final quarter of the book is decidedly dark. It seems that from 1970 or thereabouts, hierarchical order decayed, partly as the result of bureaucratic hypertrophy and partly because of instant communication on a global scale.

These last chapters are in many ways closer to long-form journalism than to what one might expect in a book that aims to reconstruct the way we write history. As such, they are lively and interesting, if variably persuasive. ‘Globalization is in crisis. Populism is on the march,’ he states. ‘Authoritarian states are ascendant. Technology … marches inexorably ahead, threatening to render most human beings redundant or immortal or both.’ The United Kingdom, meanwhile, is far from united; in particular, the commitment of Muslims to the institutions and values of liberal democracy is paper-thin. Some 43 per cent favour the introduction of sharia law, much the same as favour gender-segregated education, while a majority of Muslims in the south favour making the niqab part of school uniform for girls. How much damage this really does to the unity of the United Kingdom is anyone’s guess, however. At the very least, Ferguson has a taste for the apocalyptic that more phlegmatic readers will not share.