Critical Mass: How One Thing Leads to Another

by Philip Ball

Winner of Aventis Prize, the world's most prestigious Science book award - Phillip Ball uses the laws of physics to explain human behaviour in circumstances, as diverse as football crowds, traffic jams and stock market.

Extract:

Hobbes's masterwork, Leviathan, was an attempt to develop a political theory out of this mechanical world-view. He set himself a goal that today sounds absurdly ambitious, although at the dawn of the Enlightenment it must have seemed a natural marriage. Hobbes wanted to deduce, by logic and reason no less rigorous than that used by Galileo to understand the laws of motion, how humankind should govern itself. Starting with what he believed to be irreducible and self-evident axioms, he aimed to develop a science of human interactions, politics and society.

It is hard now to appreciate the magnitude not just of this challenge in itself, but of the shift in outlook that it embodied. There has never been any shortage of views on the best means of governance and social organization. Almost without exception, proposals before Hobbes - and many subsequently - were designed to give the proposers the greatest (perceived) advantage. Emperors, kings and queens sought to justify absolute monarchy by appeal to divine covenant. The Roman Catholic Church was hardly the first theocracy to set itself up as the sole conduit of God's authority. In Plato's Republic, one of the earliest of utopian models, cool and self-confident reasoning argued for a state in which philosophers were accorded the highest status. The rebellious English Parliament of the early 1640s demanded that the King transfer virtually all governing power to them. One could always find an argument to put oneself at the top of the pile.

Hobbes was different. What he aimed to do was to apply the method of the theoretical scientist: to stipulate fundamental first principles and see where they led him. In theory, any conclusion was possible. By analysing human nature and how people interact, he might conceivably have found that the most stable society was one based on what we would now call communism, or democracy, or fascism. In practice, Hobbes's reasoning led him towards the conclusion that he had probably preferred at the outset - from which we may be sure that his method was not as objective as he would have had the world believe. Nonetheless, its claim to have dispensed with bias and to rely only on indisputable logic is what makes Leviathan a landmark in the history of political theory.

But it is something more too. Hobbes's great work is seen today as historically and even philosophically important - but political science has become a very different beast, and no one seriously entertains the notion that Hobbes's arguments remain convincing. Nor should they, in one sense - for as we shall see, his basic postulates are very much a product of their times. Yet Leviathan is a direct and in many ways an astonishingly prescient antecedent to a revolutionary development now taking place at the forefront of modern physics. Scientists are beginning to realize that the theoretical framework that underpins contemporary physics can be adapted to describe social structures and behaviour, ranging from how traffic flows to how the economy fluctuates and how businesses are organized.

This framework is not as daunting as it might sound. Contrary to what one might imagine from the popular perception of modern physics, we do not have to delve into the imponderable paradoxes of quantum theory, or the mind-stretching revelations of relativity, or the origins of the universe in the Big Bang in order to understand the basic ideas behind these theories. No, this is an approach rooted in the behaviour of everyday substances and objects: of water, sand, magnets, crystals. But what can such things possibly have to say about the way societies organize themselves? A great deal, as it happens.

Hobbes had no inkling of any of this, but he shared the faith of today's physicists that human behaviour is not after all so complex that it cannot occasionally be understood on the basis of just a few simple postulates, or by the operation of what we might regard as natural forces. For Hobbes, contemplating the tumultuous political landscape of his country, the prime force could not be more plain: the lust for power.

THE LEVIATHAN WAKES

Thomas Hobbes had never been able to take anything for granted. His father was a poorly educated and irascible vicar, a drunkard who left his family when Thomas was sixteen and died 'in obscurity'. This put his son to little inconvenience, since from a young age Thomas was supported and encouraged by his wealthy and altogether more respectable uncle, Francis, a glover and alderman of Malmesbury. Francis watched over the boy's education, helping to nurture a clearly prodigious intellect: by the time the fourteen-year-old Thomas won admittance to Magdalen College at Oxford, he had already translated Euripides' Medea from Greek to Latin. He so excelled at the university that, when he graduated, he was recommended to the Earl of Devonshire as a tutor to the earl's son (himself only three years younger than Thomas). From such a position Hobbes was free to continue his studies of the classics. In his early twenties he acted as secretary to Francis Bacon (1561-1626), whose interests ranged from natural science and philosophy to politics and ethics. During this time, until Bacon's death, Hobbes showed no evident inclinations towards science; but Bacon's rational turn of thought left a clear imprint on his thinking.

It was not until 1629 that the forty-year-old Hobbes, a committed classicist, had his eyes opened to the power of scientific and mathematical reasoning. The story goes that Hobbes happened to glance at a book which lay open in a library, and was transfixed. The book was Euclid's Elements of Geometry, and Hobbes began to follow one of the Propositions. 'By God, this is impossible!', he exclaimed - but was soon persuaded otherwise. As Hobbes's contemporary, the gossipy biographer John Aubrey, tells it,

So he reads the Demonstration of it, which referred him back to such a Proposition; which proposition he read: that referred him back to another, which he also read, and sic deinceps [so on], that at last he was demonstratively convinced of that trueth. This made him in love with Geometry.

Hobbes was deeply impressed by how this kind of deductive reasoning, working forward from elementary propositions, allowed geometers to reach ineluctable conclusions with which all honest and percipient people would be compelled to agree. It was a prescription for certainty.

The axioms of geometry are, by and large, statements that few people would have trouble supposing. They assert such things as 'Two straight lines cannot enclose a space.' We can often convince ourselves of their validity with simple sketches. Other fields of enquiry struggle to muster analogous self-evident starting points. 'I think, therefore I am' may have convinced Descartes that, as an axiom, it is 'so solid and so certain that all the most extravagant suppositions of the sceptics were incapable of upsetting it'; but in fact every word of the sentence is open to debate, and it has none of the compelling visual power of geometry's first principles.

Hobbes was sufficiently enthused to become a would-be geometer himself, but he was never a master of the subject. Through clumsy errors he persuaded himself that he had solved the old geometric conundrum of 'squaring the circle' (a task that is in fact impossible). But that was not his principal concern. In the 1630s the tensions between Crown and Commons led Charles I to dissolve Parliament and embark on an eleven-year period of 'Personal Rule'. In the midst of an unstable society, Hobbes wanted to find a theory of governance with credentials as unimpeachable as those of Euclid's geometry. First, he needed some fundamental hypothesis about human behaviour, which in turn had to be grounded in the deepest soil of science. And there was one man who had dug deeper than any other. In the spring of 1636, Hobbes travelled to Florence to meet Galileo.

The fundamental laws describing how objects move in space are called Newton's laws, since it was Sir Isaac who first formulated them clearly. But the tallest giant from whose shoulders Newton saw afar was Galileo Galilei (1564-1642), who laid the foundations of modern mechanics. Galileo taught the world about falling bodies, which, he said, accelerate at a constant rate as they descend (if one ignores the effects of air resistance). And with his law of inertia, Galileo went beyond the 'common-sense' view of Aristotle (384-322 bc) that objects must be continually pushed if they are not to slow down: on the contrary, said Galileo, in the absence of any force an object will continue to move indefinitely in a straight line at constant velocity.

Aristotle's view is the 'common-sense' one because it is what we experience in everyday life. If you stop pedalling your bicycle, you will eventually come to a standstill. But Galileo realized that this is because frictional forces act in nature to slow us down. If we can eliminate all the forces acting on a body, including gravity and friction, the natural state of the body is motion in an unchanging direction at unchanging speed. This was a truly profound theory, for it saw beyond the practical limitations of Galileo's age to a beautiful and simple truth. (An air pump that could create a good vacuum and thus eliminate air resistance was not invented until 1654.)

Galileo's law of inertia is without doubt one of the deepest laws of nature. On meeting the great man, Hobbes became convinced that this must be the axiom he was seeking. Constant motion was the natural state of all things - including people. All human sensations and emotions, he concluded, were the result of motion. From this basic principle Hobbes would work upwards to a theory of society.

What, precisely, does Hobbes mean by this assumption? It is, to modern eyes, a cold and soulless (not to mention an obscure) description of human nature. He pictured a person as a sophisticated mechanism acted upon by external forces. This machine consists of not only the body with its nerves, muscles and sense organs, but also the mind with its imagination, memory and reason. The mind is purely a kind of calculating machine - a computer, if you will. Such machines were popular in the seventeenth century: the Scottish mathematician John Napier (1550-1617) devised one, as did the French philosopher and mathematician Blaise Pascal (1623-62). They were mechanical devices for adding and subtracting numbers; and this, said Hobbes, is all the mind does too:

When a man Reasoneth, hee does nothing else but conceive a summe totall, from Addition of parcels; or conceive a Remainder, from Subtraction of one summe from another . . . For REASON . . . is nothing but Reckoning.

The body, meanwhile, is merely a system of jointed limbs moved by the strings and pulleys of muscles and nerves. Man is an automaton.

Indeed, Hobbes held that the ingenious mechanical automata created by some inventors of the era were truly possessed of a kind of primitive life. To him there was nothing mysterious or upsetting about such an idea. Others were less sanguine: the Spanish Inquisition imprisoned some makers of automata on the grounds that they were dabbling in witchcraft and black magic.

What impelled Hobbes's mechanical people into action was not just external stimuli relayed to the brain by the apparatus of the senses. They were imbued also with an inner compulsion to remain in motion. For what is death but immobility, and which person did not seek to avoid death? 'Every man . . .', said Hobbes, 'shuns . . . death, and this he doth, by a certain impulsion of nature, no less than that whereby a stone moves downward.'

Mankind's volitions, therefore, are divided by Hobbes into 'appetites' and 'aversions': the desire to seek ways of continuing this motion and to avoid things that obstruct them. Some appetites are innate, such as hunger; others are learnt through experience. To decide on a course of action, we weigh up the relevant appetites and aversions and act accordingly.

What Hobbes means by 'motion' is a little vague, for he clearly does not intend to imply that we are forever seeking to run around at full pelt. Motion is rather a kind of liberty - a freedom to move at will. Those things that impede liberty impede motion. Even if a man sits still, the mechanism of his mind may be in furious motion: the freedom to think is an innate desire too.

What room is there in this mechanical description for free will? According to Hobbes, there is none - he was a strict determinist. Humans are puppets whose strings are pulled by the forces at play in the world. Yet Hobbes saw nothing intolerable in this bleak picture. After all, he believed that he had arrived at this basic, indisputable postulate about human nature by introspection - by considering his own nature. The first puppet he saw was himself:

whosoever looketh into himself, and considereth what he doth, when he does think, opine, reason, hope, feare, &c, and upon what grounds; he shall thereby read and know, what are the thoughts, and Passions of all other men, upon the like occasions.