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Carl Sagan -About The Development Of Objective Thinking

‘Candle in the hand’,

picture by Mustafa Almir Mahmoud at Zoonar.

Today’s sharing from the Blue House of Via-HYGEIA is an excerpt from professor Carl Sagan’s ‘The demon haunted world/Science as a candle in the dark’, Ballantine Books, 1996. Chapter 18, ‘The wind makes dust’, from pages 309 to 317. More to come.


The wind makes dust because it intends to blow, taking away our footprints.’

Specimens of Bushmen Folklore, W.H.I. Bleek and L.C. Lloyd, collectors, L.C. Lloyd, editor (1911).

‘Every time a savage tracks his game he employs a minuteness of observation, and an accuracy of inductive and deductive reasoning which, applied to other matters, would assure some reputation as a man of science… [T]he intellectual labour of a ‘good hunter or warrior’ considerably exceeds that of an ordinary Englishman.’

Thomas H. Huxley, Collected Essays, Volume II, Darwiniana: Essays (London: Macmillan, 1907), pp. 175-6- from ‘Mr Darwin’s Critics’ (1871).


Why should so many people find science hard to learn and hard to teach? I’ve tried to suggest some of the reasons – its precision, its counterintuitive and disquieting aspects, its prospects of misuse, its independence of authority, and so on. But is there something deeper? Alan Cromer is a physics professor at Northeastern University in Boston who was surprised to find so many students unable to grasp the most elementary concepts in his physics class. In Uncommon Sense: The Heretical Nature of Science (1993), Cromer proposes that science is difficult because it’s new. We, a species that’s a few hundred thousand years old, discovered the method of science only a few centuries ago, he says. Like writing, which is only a few millennia old, we haven’t gotten the hang of it yet – or at least not without very serious and attentive study. Except for an unlikely concatenation of historical events, he suggests, we would never have invented science:

This hostility to science, in the face of its obvious triumphs and benefits, is. . .evidence that it is something outside the mainstream of human development, perhaps a fluke.

Chinese civilization invented movable type, gunpowder, the rocket, the magnetic compass, the seismograph, and systematic observations and chronicles of the heavens. Indian mathematicians invented the zero, the key to comfortable arithmetic and therefore to quantitative science. Aztec civilization developed a far better calendar than that of the European civilization that inundated and destroyed it; they were better able, and for longer periods into the future, to predict where the planets would be. But none of these civilizations, Cromer argues, had developed the skeptical, inquiring, experimental method of science. All of that came out of ancient Greece:

The development of objective thinking by the Greeks appears to have required a number of specific cultural factors. First was the assembly, where men first learned to persuade one another by means of rational debate. Second was a maritime economy that prevented isolation and parochialism. Third was the existence of a widespread Greek- speaking world around which travelers and scholars could wander. Fourth was the existence of an independent merchant class that could hire its own teachers. Fifth was the Iliad and the Odyssey, literary masterpieces that are themselves the epitome of liberal rational thinking. Sixth was a literary religion not dominated by priests. And seventh was the persistence of these factors for 1,000 years. That all these factors came together in one great civilization is quite fortuitous; it didn’t happen twice.

I’m sympathetic to part of this thesis. The ancient Ionians were the first we know of to argue systematically that laws and forces of Nature, rather than gods, are responsible for the order and even the existence of the world. As Lucretius summarized their views, ‘Nature free at once and rid of her haughty lords is seen to do all things spontaneously of herself without the meddling of the gods.’ Except for the first week of introductory philosophy courses, though, the names and notions of the early Ionians are almost never mentioned in our society. Those who dismiss the gods tend to be forgotten. We are not anxious to preserve the memory of such sceptics, much less their ideas. Heroes who try to explain the world in terms of matter and energy may have arisen many times in many cultures, only to be obliterated by the priests and philosophers in charge of the conventional wisdom, as the Ionian approach was almost wholly lost after the time of Plato and Aristotle. With many cultures and many experiments of this sort, it may be that only on rare occasions does the idea take root.

Plants and animals were domesticated and civilization began only ten or twelve thousand years ago. The Ionian experiment is 2,500 years old. It was almost entirely expunged. We can see steps towards science in ancient China, India and elsewhere, even though faltering, incomplete, and bearing less fruit. But suppose the Ionians had never existed, and Greek science and mathematics never flourished. Is it possible that never again in the history of the human species would science have emerged? Or, given many cultures and many alternative historical skeins, isn’t it likely that the right combination of factors would come into play somewhere else, sooner or later – in the islands of Indonesia, say, or in the Caribbean on the outskirts of a Mesoamerican civilization untouched by Conquistadores, or in Norse colonies on the shores of the Black Sea?

The impediment to scientific thinking is not, I think, the difficulty of the subject. Complex intellectual feats have been mainstays even of oppressed cultures. Shamans, magicians and theologians are highly skilled in their intricate and arcane arts. No, the impediment is political and hierarchical.

In those cultures lacking unfamiliar challenges, external or internal, where fundamental change is unneeded, novel ideas need not be encouraged.

Indeed, heresies can be declared dangerous; thinking can be rigidified; and sanctions against impermissible ideas can be enforced – all without much harm. But under varied and changing environmental or biological or political circumstances, simply copying the old ways no longer works. Then, a premium awaits those who, instead of blandly following tradition, or trying to foist their preferences on to the physical or social Universe, are open to what the Universe teaches. Each society must decide where in the continuum between openness and rigidity safety lies.

Greek mathematics was a brilliant step forward. Greek science, on the other hand – its first steps rudimentary and often uninformed by experiment – was riddled with error.

Despite the fact that we cannot see in pitch darkness, they believed that vision depends on a kind of radar that emanates from the eye, bounces off what we’re seeing, and returns to the eye.

(Nevertheless, they made substantial progress in optics.) Despite the obvious resemblance of children to their mothers, they believed that heredity was carried by semen alone, the woman a mere passive receptacle.

They believed that the horizontal motion of a thrown rock somehow lifts it up, so that it takes longer to reach the ground than a rock dropped from the same height at the same moment.

Enamoured of simple geometry, they believed the circle to be ‘perfect’; despite the ‘Man in the Moon’ and sunspots (occasionally visible to the naked eye at sunset), they held the heavens also to be ‘perfect’; therefore, planetary orbits had to be circular.

Being freed from superstition isn’t enough for science to grow. One must also have the idea of interrogating Nature, of doing experiments. There were some brilliant examples-Eratosthenes’s measurements of the Earth’s diameter, say, or Empedocles’s clepsydra experiment demonstrating the material nature of air. But in a society in which manual labour is demeaned and thought fit only for slaves, as in the classical Graeco-Roman world, the experimental method does not thrive. Science requires us to be freed of gross superstition and gross injustice both. Often, superstition and injustice are imposed by the same ecclesiastical and secular authorities, working hand in glove. It is no surprise that political revolutions, skepticism about religion, and the rise of science might go together. Liberation from superstition is a necessary but not a sufficient condition for science.

At the same time, it is undeniable that central figures in the transition from medieval superstition to modern science were profoundly influenced by the idea of one Supreme God who created the Universe and established not only commandments that humans must live by, but laws that Nature itself must abide by. The seventeenth century German astronomer Johannes Kepler, without whom Newtonian physics might not have come to be, described his pursuit of science as a wish to know the mind of God. In our own time, leading scientists, including Albert Einstein and Stephen Hawking, have described their quest in nearly identical terms. The philosopher Alfred North Whitehead and the historian of Chinese technology Joseph Needham have also suggested that what was lacking in the development of science in non-western cultures was monotheism.

And yet, I think there is strong contrary evidence to this whole thesis, calling out to us from across the millennia…

The small hunting party follows the trail of hoofprints and other spoor. They pause for a moment by a stand of trees. Squatting on their heels, they examine the evidence more carefully. The trail they’ve been following has been crossed by another. Quickly they agree on which animals are responsible, how many of them, what ages and sexes, whether any are injured, how fast they’re travelling, how long ago they passed, whether any other hunters are in pursuit, whether the party can overtake the game, and if so, how long it will take. The decision made, they flick their hands over the trail they will follow, make a quiet sound between their teeth like the wind, and off they lope. Despite their bows and poison arrows, they continue at championship marathon racing form for hours. Almost always they’ve read the message in the ground correctly. The wildebeests or elands or okapis are where they thought, in the numbers and condition they estimated. The hunt is successful. Meat is carried back to the temporary camp. Everyone feasts.

This more or less typical hunting vignette comes from the !Kung San people of the Kalahari Desert, in the Republics of Botswana and Namibia, who are now, tragically, on the verge of extinction. But for decades they and their way of life were studied by anthropologists. The !Kung San may be typical of the hunter-gatherer mode of existence in which we humans spent most of our time, until ten thousand years ago, when plants and animals were domesticated and the human condition began to change, perhaps forever. They were trackers of such legendary prowess that they were enlisted by the apartheid South African army to hunt down human prey in the wars against the ‘front-line states’. This encounter with the white South African military in several different ways accelerated the destruction of the !Kung San way of life. It had, in any case, been deteriorating bit by bit over the centuries from every contact with European civilization.

How did they do it? How could they tell so much from barely more than a glance? Saying they’re keen observers explains nothing. What actually did they do? According to anthropologist Richard Lee:

They scrutinized the shape of the depressions. The footprints of a fast-moving animal display a more elongated symmetry. A slightly lame animal favours the afflicted foot, puts less weight on it, and leaves a fainter imprint. A heavier animal leaves a deeper and broader hollow. The correlation functions are in the heads of the hunters.

In the course of the day, the footprints erode a little. The walls of the depression tend to crumble. Windblown sand accumulates on the floor of the hollow. Perhaps bits of leaf, twigs or grass are blown into it. The longer you wait, the more erosion there is.

This method is essentially identical to what planetary astronomers use in analysing craters left by impacting worldlets: other things being equal, the shallower the crater, the older it is. Craters with slumped walls, with modest depth-to-diameter ratios, with fine particles accumulated in their interiors tend to be more ancient, because they had to be around long enough for these erosive processes to come into play.

The sources of degradation may differ from world to world, or desert to desert, or epoch to epoch. But if you know what they are you can determine a great deal from how crisp or blurred the crater is. If insect or other animal tracks are superposed on the hoofprints, this also argues against their freshness. The subsurface moisture content of the soil and the rate at which it dries out after being exposed by a hoof determine how crumbly the crater walls are. All these matters are closely studied by the !Kung.

The galloping herd hates the hot Sun. The animals will use whatever shade they can find. They will alter course to take brief advantage of the shade from a stand of trees. But where the shadow is depends on the time of day, because the Sun is moving across the sky. In the morning, as the Sun is rising in the east, shadows are cast west of the trees. Later in the afternoon, as the Sun is setting toward the west, shadows are cast to the east. From the swerve of the tracks, it’s possible to tell how long ago the animals passed. This calculation will be different in different seasons of the year. So, the hunters must carry in their heads a kind of astronomical calendar predicting the apparent solar motion.

To me, all of these formidable forensic tracking skills are science in action.

Not only are hunter-gatherers expert in the tracks of other animals; they also know human tracks very well. Every member of the band is recognizable by his or her footprints; they are as familiar as their faces. Laurens van der Post recounts:

Many miles from home and separated from the rest, Nxou and I, on the track of a wounded buck, suddenly found another set of prints and spoor joining our own. He gave a deep grunt of satisfaction and said it was Bauxhau’s foot- marks made not many minutes before. He declared Bauxhau was running fast and that we would soon see him and the animal. We topped the dune in front of us and there was Bauxhau, already skinning the animal.’

Or Richard Lee, also among the !Kung San, relates how when briefly examining some tracks a hunter commented, ‘Oh, look, Tunu is here with his brother-in-law. But where is his son?

Is this really science? Does every tracker in the course of his training sit on his haunches for hours, following the slow degradation of an eland hoofprint? When the anthropologist asks this question, the answer given is that hunters have always used such methods. They observed their fathers and other accomplished hunters during their apprenticeships. They learned by imitation. The general principles were passed down from generation to generation. The local variations – wind speed, soil moisture – are updated as needed in each generation, or seasonally, or day-by-day.

But modern scientists do just the same. Every time we try to judge the age of a crater on the Moon or Mercury or Triton by its degree of erosion, we do not perform the calculation from scratch. We dust off a certain scientific paper and read the tried-and-true numbers that have been set down perhaps as much as a generation earlier. Physicists do not derive Maxwell’s equations or quantum mechanics from scratch. They try to understand the principles and the mathematics, they observe its utility, they note how Nature follows these rules, and they take these sciences to heart, making them their own.

Yet someone had to figure out all these tracking protocols for the first time, perhaps some Paleolithic genius, or more likely a succession of geniuses in widely separated times and places. There is no hint in the !Kung tracking protocols of magical methods – examining the stars the night before or the entrails of an animal, or casting dice, or interpreting dreams, or conjuring demons, or any of the myriad other spurious claims to knowledge that humans have intermittently entertained. Here there’s a specific, well- defined question: which way did the prey go and what are its characteristics? You need a precise answer that magic and divination simply do not provide, or at least not often enough to stave off starvation. Instead, hunter-gatherers – who are not very superstitious in their everyday life, except during trance dances around the fire and under the influence of mild euphoriants – are practical, workaday, motivated, social, and often very cheerful. They employ skills winnowed from past successes and failures.

Scientific thinking has almost certainly been with us from the beginning. You can even see it in chimpanzees when tracking on patrol of the frontiers of their territory, or when preparing a reed to insert into the termite mound to extract a modest but much- needed source of protein. The development of tracking skills delivers a powerful evolutionary selective advantage. Those groups unable to figure it out get less protein and leave fewer offspring. Those with a scientific bent, those able patiently to observe, those with a penchant for figuring out acquire more food, especially more protein, and live in more varied habitats; they and their hereditary lines prosper. The same is true, for instance, of Polynesian seafaring skills. A scientific bent brings tangible rewards.

The other principal food-garnering activity of pre-agrarian societies is foraging. To forage, you must know the properties of many plants, and you must certainly be able to distinguish one from another. Botanists and anthropologists have repeatedly found that all over the world hunter-gatherer peoples have distinguished the various plant species with the precision of western taxonomists. They have mentally mapped their territory with the finesse of cartographers. Again, all this is a precondition for survival.

So the claim that, just as children are not developmentally ready for certain concepts in mathematics or logic, so ‘primitive’ peoples are not intellectually able to grasp science and technology, is nonsense. This vestige of colonialism and racism is belied by the everyday activities of people living with no fixed abode and almost no possessions, the few remaining hunter-gatherers – the custodians of our deep past.

Of Cromer’s criteria for ‘objective thinking’, we can certainly find in hunter-gatherer peoples vigorous and substantive debate, direct participatory democracy, wide-ranging travel, no priests, and the persistence of these factors not for 1,000 but for 300,000 years or more. By his criteria hunter-gatherers ought to have science. I think they do. Or did.

What Ionia and ancient Greece provided is not so much inventions or technology or engineering, but the idea of systematic inquiry, the notion that laws of Nature, rather than capricious gods, govern the world. Water, air, earth and fire all had their turn as candidate ‘explanations’ of the nature and origin of the world. Each such explanation – identified with a different pre-Socratic philosopher – was deeply flawed in its details. But the mode of explanation, an alternative to divine intervention, was productive and new. Likewise, in the history of ancient Greece, we can see nearly all significant events driven by the caprice of the gods in Homer, only a few events in Herodotus, and essentially none at all in Thucydides. In a few hundred years, history passed from god-driven to human-driven.

Something akin to laws of Nature were once glimpsed in a determinedly polytheistic society, in which some scholars toyed with a form of atheism. This approach of the pre-Socratics was, beginning in about the fourth century BC, quenched by Plato, Aristotle and then Christian theologians. If the skein of historical causality had been different – if the brilliant guesses of the atomists on the nature of matter, the plurality of worlds, the vastness of space and time had been treasured and built upon, if the innovative technology of Archimedes had been taught and emulated, if the notion of invariable laws of Nature that humans must seek out and understand had been widely propagated – I wonder what kind of world we would live in now.

I don’t think science is hard to teach because humans aren’t ready for it, or because it arose only through a fluke, or because, by and large, we don’t have the brainpower to grapple with it.

Instead, the enormous zest for science that I see in first-graders and the lesson from the remnant hunter-gatherers both speak eloquently: a proclivity for science is embedded deeply within us, in all times, places and cultures. It has been the means for our survival. It is our birthright.

When, through indifference, inattention, incompetence, or fear of skepticism, we discourage children from science, we are disenfranchising them, taking from them the
tools needed to manage their future.

American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. Sagan advocated scientific skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI). He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies.


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Carl Sagan -About The Development Of Objective Thinking

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