Park travelled on down the river as far as Silla, where, exhausted, he decided to turn back short of Timbuctoo on 25 August 1796. On the return journey he was robbed and stripped by Moorish banditti in ‘a dark wood’ before he reached Kalamia. They took everything — his horse, his compass, his hat, all his clothes except his trousers and his battered boots (‘the sole of one of them was tied onto my foot with a broken bridle rein’). They had evidently intended to kill him, but saw him as a feeble white man beneath contempt. They did however throw his hat back to him — not realising that it contained the papers of his travel journal folded up in the band. In what became another famous passage, Park described sitting down in utter despair, believing that the end had come. ‘After they were gone, I sat for sometime looking round me with amazement and terror … I saw myself in a vast wilderness in the depth of the rainy season, naked and alone; surrounded by savage animals, and men still more savage. I was 500 miles from the nearest European settlement. All these circumstances crowded at once on my recollection; and I confess my spirits began to fail me. I considered my fate as certain, and that I had no alternative, but to lie down and perish.’

Park’s thoughts turned helplessly towards prayer, and ‘the protecting eye of Providence’. But then something curious happened. As he hung his head in utter exhaustion and misery, his gaze began listlessly wandering over the bare ground at his feet. He noticed a tiny piece of flowering moss pushing up through the stony earth beside his boot. In a flash, his scientific interest was aroused, and leaning forward to examine the minute plant, for one moment he forgot his terrible situation. He carefully described this movement out of paralysing despair: At this moment, painful as my reflections were, the extraordinary beauty of a small moss in fructification, irresistibly caught my eye. I mention this to show from what trifling circumstances the mind will sometimes derive consolation; for though the whole plant was not larger than the top of one of my fingers, I could not contemplate the delicate conformation of its roots, leaves, and capsula, without admiration.’

In that moment of pure scientific wonder, Park’s thoughts and outlook were transformed: ‘Can the Being (thought I) who planted, watered, and brought to perfection, in this obscure part of the world, a thing which appears of so small importance, look with unconcern upon the situation and suffering of creatures formed after his own image? — surely not! Reflections like these would not allow me to despair. I started up, and disregarding both hunger and fatigue, travelled forwards, assured that relief was at hand; and I was not disappointed.’

According to legend, the first mathematical formulation of what we might today call a law of nature dates back to an Ionian named Pythagoras (ca. 580 BC-ca. 490 bc), famous for the theorem named after him: that the square of the hypotenuse (longest side) of a right triangle equals the sum of the squares of the other two sides. Pythagoras is said to have discovered the numerical relationship between the length of the strings used in musical instruments and the harmonic combinations of the sounds. In today's language we would describe that relationship by saying that the frequency—the number of vibrations per second—of a string vibrating under fixed tension is inversely proportional to the length of the string. From the practical point of view, this explains why bass guitars must have longer strings than ordinary guitars. Pythagoras probably did not it really discover this—he also did not discover the theorem that bears his name—but there is evidence that some relation between string length and pitch was known in his day If so, one could call that simple mathematical formula the first instance of what we now know as theoretical physics.

Apart from the Pythagorean law of strings, the only physical laws known correctly to the ancients were three laws detailed by Archimedes (ca. 287 BC-ca. 212 bc), by far the most eminent physicist of antiquity. In today's terminology, the law of the lever explains that small forces can lift large weights because the lever amplifies a force according to the ratio of the distances from the lever's fulcrum. The law of buoyancy states that any object immersed in a fluid will experience an upward force equal to the weight of the displaced fluid. And the law of reflection asserts that the angle between a beam of light and a mirror is equal to the angle between the mirror and the reflected beam. But Archimedes did not call them laws, nor did he explain them with reference to observation and measurement. Instead he treated them as if they were purely mathematical theorems, in an axiomatic system much like the one Euclid created for geometry.

As the Ionian influence spread, there appeared others who saw that the universe possesses an internal order, one that could be understood through observation and reason. Anaximander (ca. 6io BC-ca. 546 bc), a friend and possibly a student of Thales, argued that since human infants are helpless at birth, if the first human had somehow appeared on earth as an infant, it would not have survived. In what may have been humanity's first inkling of evolution, people, Anaximander reasoned, must therefore have evolved from other animals whose young are hardier. In Sicily, Empedocles (ca. 490 BC-ca. 430 bc) observed the use of an instrument called a clepsydra. Sometimes used as a ladle, it consisted of a sphere with an open neck and small holes in its bottom. When immersed in water it would fill, and if the open neck was then covered, the clepsydra could be lifted out without the water in it falling through the holes. Empedocles noticed that if you cover the neck before you immerse it, a clepsydra does not fill. He reasoned that something invisible must be preventing the water from entering the sphere through the holes—he had discovered the material substance we call air.

Around the same time Democritus (ca 460 BC-ca. 370 bc). from an Ionian colony in northern Greece, pondered what happened when you break or cut an object into pieces. He argued that you ought not to be able to continue the process indefinitely. Instead he postulated that everything, including all living beings. is made of fundamental particles that cannot be cut or broken into parts. He named these ultimate particles atoms, from the Greek adjective meaning "uncuttable." Democritus believed that every material phenomenon is a product of the collision of atoms. In his view, dubbed atomism, all atoms move around in space, and, unless disturbed, move forward indefinitely. Today that idea is called the law of inertia.

The revolutionary idea that we are but ordinary inhabitants of the universe, not special beings distinguished by existing at its center, was first championed by Aristarchus (ca. 310 BC-ca. 230 BC), one of the last of the Ionian scientists. Only one of his calculations survives, a complex geometric analysis of careful observations he made of the size of the earth's shadow on the moon during a lunar eclipse. He concluded from his data that the sun must be much larger than the earth. Perhaps inspired by the idea that tiny objects ought to orbit mammoth ones and not the other way around, he became the first person to argue that the earth is not the center of our planetary system, but rather that it and the other planets orbit the much larger sun. It is a small step from the realization that the earth is just another planet to the idea that our sun is nothing special either. Aristarchus suspected that this was the case and believed that the stars we see in the night sky are actually nothing more than distant suns.

The Ionians were but one of many schools of ancient Greek philosophy, each with different and often contradictory traditions. Unfortunately, the Ionians' view of nature—that it can be explained through general laws and reduced to a simple set of principles—exerted a powerful influence for only a few centuries. One reason is that Ionian theories often seemed to have no place for the notion of free will or purpose, or the concept that gods intervene in the workings of the world. These were startling omissions as profoundly unsettling to many Greek thinkers as they are to many people today. The philosopher Epicurus (341 BC-270 bc), for example, opposed atomism on the grounds that it is "better to follow the myths about the gods than to become a 'slave' to the destiny of natural philosophers." Aristotle too rejected the concept of atoms because he could not accept that human beings were composed of soulless, inanimate objects. The Ionian idea that the universe is not human-centered was a milestone in our understanding of the cosmos, but it was an idea that would b dropped and not picked up again, or commonly accepted, until Galileo, almost twenty centuries later.

When I see the butterfly, I imagine in my mind's eye the extraordinary chemical machinery of life, the winding loom of he DNA, the proteins linking like lock and key, the ceaseless hubbub of molecular commerce that goes on behind the scenes, from egg, to caterpillar, to chrysalis, to adult. Surely, no land of faerie is more magical than the transformation that occurs in the chrysalis, when a creepy-crawly caterpillar curls up in a self-made sack and rearranges its molecules to emerge as a winged beauty.