Consciousness is a nonphysical property that cannot be defined in physical terms, and indeed does not exist in the physical universe. It is impossible to determine by any physical means if an object is conscious. When presented with miscellaneous objects, such as an orange, a chair, a clock, a human being, a candle flame, and a crystal, an experimenter cannot determine by means of experiments with physical equipment which of these objects is conscious. This normally would constitute sufficient proof that consciousness does not exist anywhere in any form. One of the objects, however, could be myself, and I know beyond all doubt that I am a conscious being. I am more certain of my consciousness than was Dr. Johnson of the concreteness of his stone. Consciousness beyond all doubt exists, yet demonstrably does not exist in the physical universe. Consciousness belongs to the Universe not the physical universe. No other conclusion seems possible.

Everything is spread out in time. Things stretch away into the recent past as recalled in our memories and newspapers, and into the distant past as recounted by historians and geologists. They also stretch away into the near future as anticipated in our plans and foretold by fortune tellers, and into the distant future as predicted by geologists and astronomers.

Say no more of time! If you want a peaceful mind go no farther. Every step in quest of understanding time leads to greater bewilderment. Much of the problem is that our languages inadequately express our experiences of time.

“What, then, is time?” asked Augustine of Hippo in the Confessions. “If no one asks me, I know what it is. If I wish to explain what it is to him who asks me, I do not know.” He viewed time as a continuous temporal sequence from the past to the future, from Creation in the beginning to Judgment in the end. Time thus displays a historiography ordained by either God, fate, or natural law. This is much the same as our present commonsense general view. It caused him much perplexity, some of which is expressed by Austin Dobson in The Paradox of Time:

Some of the problem is easily stated: Nothing displayed in time can change! If you think of time in terms of space, as an extension, a sort of one-dimensional space, with everything displayed in it, such as birthdays, anniversaries, holidays, then everything has its fixed moment in time and cannot possibly change.

We have a picture of a seamless spacetime projecting into the space and time of each observer's world line. Though elegant and economic, in one sense it differs little from the Newtonian picture. Space in the Newtonian scheme was just a sort of nothing (a sideless box) spanning everything, and time was a similar sort of nothing in which everything also had location. In the theory of special relativity both came together to form an expanse of spacetime containing everything that again was just a sort of nothing (just a bigger sideless box).

Then in 1916 Einstein advanced the theory of general relativity and the picture changed dramatically. (How dramatically was not fully realized for many years.) Spacetime lost its state of nothingness and acquired a tangible physical reality. Gravity ceased to be a mysterious astral force acting instantaneously at a distance and became a property of dynamic curved spacetime.

In the new scheme spacetime itself guides the heavenly bodies and the old astrological action at a distance turned out to be the curvature of space and time combined into spacetime. We now have a spacetime that pulls and pushes and transmits shivers and shakes at the speed of light. We cannot eat spacetime, but it can be hit, and can hit back, and can eat us if we stray too close to a black hole. Spacetime in general relativity springs to life and becomes an active participant in the physical universe.

In the preface to the first edition of Masks of Universe I wrote: “At first I thought this book would take me only a few months to write. After all, the basic idea was simple, and only a few words should suffice to make it clear and convincing. But soon this illusion was shattered. A few months grew into three years, and now I realize that thirty years would not suffice. But enough! Other work presses, and life is too short.” Here I am, not thirty years but almost two decades later writing the preface to the second edition and struggling again to make clear the “simple idea.”

The idea rests on the distinction between Universe and universes. The Universe by definition is everything and includes us experiencing and thinking about it. The universes are the models of the Universe that we construct to explain our observations and experiences. Beneath the deceptive simplicity of this idea lies a little-explored realm of thought.

No person can live in a society of intelligent members unless equipped with grand ideas of the world around. These grand ideas – or cosmic formulations – establish the universe in which that society lives. The universes that human beings devise and in which they live, or believe they live, organize and give meaning to their experiences.

The Universe is everything. It includes us and the rational universes we collectively devise. Each universe unifies a society and dictates the “true” facts. Individuals suppose with unfailing confidence that their particular universe is the Universe, and their confidence is not in the least shaken by the fact that our ancestors lived in very different universes and our descendants in the future will live also in totally different universes. In all universes things have their causes, often hidden from ordinary mortals. We depend on our wise men – emperors, kings, shamans, priests, sages, prophets, and professors – to put us right and tell us the “true” facts. As long as somebody reliable knows the truth, all is right with the universe.

All universes have their rules of containment that define what is included as fitting and what is excluded as unfitting. Thales said the Ionian universe consisted of water; Anaximenes said air; Heraclitus said fire; Xenophanes said earth; Empedocles said earth, water, air, and fire. Democritus said the Atomist universe consisted only of atoms and the void; all else was illusion and opinion. Plato said the Platonic universe consisted of the eternal verities of the Mind; all else was shadow and deception. Aristotle said the Aristotelian universe consisted of earth, water, air, fire, and ether in ascending order, animated by Ideas, and nothing existed beyond the sphere of the stars. Saint Augustine said the Christian universe consisted of the Word of God, and all else was heresy.

The telescope, microscope, thermometer, barometer, precision clock, air pump, and other seventeenth-century inventions preceded the Age of Reason in the eighteenth century. The age of enlightened reason commenced with prophets proclaiming visions of a new universe: “I feel engulfed in the infinite immensity of spaces whereof I know nothing and which know nothing of me, I am terrified. … The eternal silence of these infinite spaces alarms me,” said Blaise Pascal. And “behold a universe so immense that I am lost in it. I no longer know where I am. I am just nothing at all. Our world is terrifying in its insignificance,” said Bernard de Fontenelle.

The mechanistic universe of the eighteenth century more than fulfilled the promise of the prophets. Outfitted with laws uniting the Earth and the heavens, with self-running celestial mechanistic systems distributed throughout endless space, with time ticking away regularly as in Huygens's precision pendulum clock, the mechanistic universe opened up the prospect of the human mind able at last to solve all the riddles of nature.

Lofty thoughts that formerly soared among the towers of the Eternal City descended to street level in an exhilarating new Earthly City. Pious otherworldly preoccupations transformed into practical worldly occupations. The reborn world was bright and young, free of the late medieval conviction that all was senile and exhausted. The rejuvenated human sciences, led by “lapsed Christians,” surged forward, achieving reforms that nowadays we take for granted as characteristic of Western society.

We take space and time for granted. Normally they do not trouble us, yet whenever we think about them we become puzzled.

Space seems simple enough. Here it is, all around us, stretching away and spanning everything in the external world. We are surprised when told that people in other cultures have different ways of regarding space. What is there about it that can possibly be different? Edward Hall in The Hidden Dimension says, “there is no alternative to accepting the fact that people reared in different cultures live in different sensory worlds” – in other worlds of space. It seems that the Arabs, Japanese, Hopi, and the people of many other cultures have different modes of expression concerning arrangements and relations in space; they live in different mental worlds – in other worlds of space.

Time is much more puzzling. Here it is in our imagination, stretching away, spanning everything in the past, present, and future. But unlike space it is not all around us and directly accessible. We experience time within ourselves, it seems, and cannot perceive it directly in the external world. Those intervals of minutes and hours on the face of a clock are actually intervals of space. A second cannot be displayed directly in pure form in the external world in the same way as a centimeter.

We live in the Solar System on the planet Earth that revolves with other planets around a star called the Sun. Light from the Sun hurrying at great speed takes 500 seconds to reach the Earth and five hours to reach the far-flung planet Pluto. The Earth that to us seems large is dwarfed by the Solar System with its whirling planets.

Starlight from the nearest stars travels for years before reaching the Earth. If we imagine the Sun having the size of a grain of sand, the nearby stars on the same scale would be at a distance of one hour's drive on an interstate highway. Scattered out to enormous distances in all directions are a hundred billion stars that constitute the whirlpool system called our Galaxy. The Galaxy – a glittering carousel of stars across which light takes 100,000 years to travel and around which the Sun journeys once every 200 million years – seems incomprehensibly large compared with the solar system.

Much has been discovered about the Galaxy: its many kinds of stars, sunlike stars, blue, yellow, and red giants, binary stars, white dwarfs, and dense neutron stars; its great spiral disk seen by us as the Milky Way where clouds of glowing gas and obscuring dust give birth to new stars; its even greater halo of very old stars and globular clusters; and still much that remains to be discovered.

Newton's universe of uniformly distributed stars has become Wright's universe.

Etienne Tempier, Bishop of Paris, roundly condemned all who dared to trifle with the power of the supreme being. Scholars and divines were free to admit reason into matters of faith provided full acknowledgment was made to God as an all-powerful being free of self-contradiction. Here was the Trojan Horse, introduced by the well-intentioned bishop, from which sallied forth in years to come thoughts that would topple the towers of the medieval universe.

Professors at Oxford and Paris in the fourteenth century made great progress in clarifying the nature of space, time, and motion. William Heytesbury and his colleagues at Merton College defined velocity and acceleration and then succeeded in calculating by graphical methods the distance traveled in an interval of time by a body having constant acceleration. William of Ockham participated in these studies while fighting a battle against needless abstractions. His celebrated principle of theoretical parsimony – known as Ockham's razor – states that in the use of concepts “it is foolish to accomplish with a greater number what can be done with fewer.”

Jean Buridan, a professor at Paris and formerly Ockham's student, revived the notion of impetus that can be traced back to Hipparchus in the second century B.C. and is now referred to as momentum. According to Buridan, impetus is proportional to the velocity of a body and also its quantity of matter (now referred to as mass), and the impetus of a thrown body maintains the body in a state of motion.

An unidentified English author of the fourteenth century, who was probably a priest, wrote

Like other contemplative mystics of the Middle Ages the author discovered that thought could not unveil the face of God: “By love may he be gotten and holden; but by thought neither.” God, the Cloud of Unknowing, was beyond articulation, and the source of all articulations.

Contemplative mystics in the Middle Ages – Christian, Jewish, and Muslim – ranked among the most advanced thinkers of their time. Thus, Nicholas of Cusa, prince and statesman of the Roman Church, sagely recorded that “scientific superstition” is the expectation that science answers our every question.

In the West, and wherever else the modern physical universe now holds sway, sections of the public have caught up with the agnostic intellectuals of the nineteenth century.

In his work On Learned Ignorance, written in 1440, Cardinal Nicholas of Cusa argued that although the darkness of “unlearned ignorance” disperses in the light of growing knowledge, there is another side to ignorance, which he called “learned ignorance,” that grows with knowledge. “No man, not even the most learned in his discipline, can progress farther along the road to perfection than the point where he is found most knowing in the very ignorance that embraces him; and he will be the more learned the more he comes to know himself for ignorant.”

Consider the unlearned person, unaware of his ignorance, who thinks he knows everything! As knowledge increases, ignorance decreases, yet this kind of ignorance – unlearned ignorance – is merely the absence of knowledge. With knowledge comes an awareness of ignorance – learned ignorance – and the more a person knows, the more aware that person becomes of what he does not know. Learned and unlearned ignorance are like day and night.

The principle of learned ignorance at first comes as a surprise. “Knowledge is power” says the proverb. We acquire learning seeking to extend the horizon of our knowledge. Education uplifts the mind and dispels ignorance. Issues that arise in the learning process that at first are puzzling are subsequently resolved in the corpus of greater knowledge. But, as the learned cardinal said, the penalty of knowledge is doubt.

Four thousand years ago the Babylonian sky-watchers charted the heavens, divided the sky into constellations of the zodiac, compiled star catalogs, recorded the movements of planets, prepared calendars, and predicted eclipses. Although skilled in the arts of computation, the Babylonians did not theorize on the laws of celestial motion for they were not scientists but priests paying homage to the sky gods of the mythic universe.

Between the seventh and sixth centuries B.C. intellectual activity quickened in many lands. The teachings of Zoroaster in Persia, Gautama the Buddha and Mahavira the Jain in India, and Confucius and Lao-tzu in China gave birth to ethical doctrines and inspired religions of virtuous living. Meanwhile in the Hellenic world an intellectual movement of a different stamp had begun that would also lead to eventful consequences.

The Greek civilization of scattered cities and colonies formed a mosaic of cultures that nurtured an elasticity of mind. Hellenic philosopher–scientists of the sixth century B.C. developed a style of thought radically different from the mystery-mongering of the Babylonian and Egyptian astrologer–priests. The Greeks awoke the dead matter of the mythic universe. They disentangled the sequences of cause and effect in a world of natural happenings. They looked askance at the sacred myths, developed the rudiments of the scientific method, and to this day science inherits their curiosity and incredulity.

It began with the Ionians, descendants of the Mycenaeans, who inherited the Minoan culture of Crete.

In the tenth and eleventh centuries the Arab dialecticians of the Kalam (the Mutakallimun) were opposed to the Aristotelian science in Muslim theology and professed a theory of extreme theism. Everything, they said, is governed by the will of the Sole Agent. They exalted the power of the Sole Agent by squeezing dry the natural world of all ability to be self-explanatory. The Mutakallimun devised their own interpretation of the atomism of the Epicureans. The Kalam atoms were completely isolated and noninteracting. Not only matter but space also was atomized. Nothing bridged the atomic gulfs except the harmonizing and coordinating power of the Sole Agent.

Al-Bakillani, a disciple of a disciple of the famed al-Ashari (the founder of Muslim scholasticism), lived in Baghdad where he died in 1013. He introduced the idea of atomic time. His ideas were critically discussed in the twelfth century by Moses Maimonides in The Guide for the Perplexed. “An hour,” explained Maimonides, “is divided into sixty minutes, the minute into sixty seconds, the second into sixty parts, and so on; at last after ten or more successive divisions by sixty, time-elements are obtained, which are not subjected to division, and in fact are indivisible, just as is the case with space.”

In al-Bakillani's scheme, atoms divided up space and time. The universe, without continuity in space and time, manifestly was under the coordinating control of the Sole Agent. In an atom of time the universe exists in a fixed state of being.

“History is only a pack of tricks we play on the dead,” said Voltaire. By scanning history, peering into prehistory, we seek the ancestral incunabula. With meddlesome curiosity we turn over stones, dig up bones, and expect the dead of long ago to forgive the tricks we play.

At least we have learned not to portray early human beings as shambling Nibelungs, or as Hobbesian ogres, “solitary, poor, nasty, brutish, and short.” Doubtless the forgotten people of the distant past were thoughtful beings, with a spring in their stride and light in their eyes, who ornamented their bodies, bedecked their dead with flowers, danced, sang, laughed, cried, and, like us, had their joys and sorrows. They lacked our knowledge, yet had instead their own, perhaps more than we can ever realize.

Little is known of the early people who lived hundreds of thousands of years ago. Their lifestyle was certainly primitive by our standards and even by the standards of the African Bushmen and Australian Aborigines. Other than a miscellany of skulls and skeletal remains, tool kits, artifacts, and evidence of diet, we have precious little information on how the early people lived, and none whatever on how they thought. But we know they had brains as large as ours and we may safely assume that their brains, like ours, were fully functional. The universe in which the early people lived, or thought they lived, is lost forever, and all our reconstructions are possibly in error.