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.

The theme of this book is that the universe in which we live, or think we live, is mostly a thing of our own making. The underlying idea is the distinction between Universe and universes. It is a simple idea having many consequences.

The Universe is everything. What it is, in its own right, independent of our changing opinions, we never fully know. It is all-inclusive and includes us as conscious beings. We are a part or an aspect of the Universe experiencing and thinking about itself.

What is the Universe? Seeking an answer is the endless quest. I can think of no better reply than the admission by Socrates: “all that I know is that I know nothing.” David Hume, a Scottish philosopher in the eighteenth century, in reply to a similar question, said “it admits of no answer” for absolute truth is inaccessible to the human mind. Logan Smith, an expatriate American living in London, expressed his reply in a witty essay Trivia (1902), “I awoke this morning … into the daylight, the furniture of my bedroom – in fact, into the well-known, often-discussed, but to my mind as yet unexplained Universe.”

The universes are our models of the Universe. They are great schemes of intricate thought – grand belief systems – that rationalize the human experience.

Francis Bacon, English courtier and statesman of the late sixteenth and early seventeenth centuries, promoted a philosophy of empirical science and declared, “let every student of nature take this as his rule: that whatever the mind seizes upon with particular satisfaction is to be held in suspicion.” His strong belief in empirical methods of inquiry assured him that witches existed.

Let us look at the witch universe in which this incredulous and illustrious man lived.

Tracing the development of ideas in the long Middle Ages leads the student into a bewildering labyrinth of astonishing beliefs. The works of Jabir ibn Haiyan, court physician in the eighth century to Harun al-Rashid (the caliph of Baghdad famed in The Thousand and One Nights), became widely known for their medical lore and learned alchemy. Jabir was later latinized into Geber, and because of the rigmarole and obfuscation of the numerous works attributed to him, the word Geberish became eventually gibberish.

In the Middle Ages the telluric elements of earth, water, air, and fire exhibited respectively the qualities of cold, wet, dry, and hot. By erudite argumentation the elements accounted for bodily humors of melancholy, phlegm, choler, and blood, which in a marvelous manner corresponded with the characteristics of creation, fall, redemption, and judgment. Acts of the will were governed by God, acts of the intellect by angels, and acts of the body by the celestial orbs. Each person possessed a daemon or genius who acted as a guiding spirit.

“I drew these tides of men into my hands and wrote my will across the sky in stars,” wrote Lawrence of Arabia in The Seven Pillars of Wisdom. Human tides have washed across the globe, crushing nations and carving out empires, led by god-possessed men who sought to write their will across the sky in stars. One such leader was Alexander the Great, who crossed the Hellespont with his cohorts in the fourth century B.C., subjugated Asia Minor and Egypt, vanquished the armies of the Persian Empire, quelled the turbulent forces of Afghanistan, crossed the Hindu Kush, and invaded and defeated the nations of the Punjab.

Eastward flowed Hellenic philosophy and science in the wake of Alexander's conquests; westward flowed oriental philosophy and religion. Westward into the Mediterranean world came the glorious Ahura Mazda – the Zoroastrian Lord of Light embattled with the Lord of Darkness – bringing the belief that the soul is divine and the worship of gods other than the true god a sin. Westward into the Roman legions came the religion of the dying and resurrected martyred god, the triumphant Mithras, bringing the sacramental eating of the flesh of the god and the notions of forgiveness and redemption. Westward came the Babylonian stories of the creation and the flood, the Persian stories of heaven and hell, the last day of judgment, and the resurrection of the dead, all of which shaped the theology and philosophy of the Greco-Roman world in preparation for the rise of Christianity and Islam.

In everyday life we deal with things of sensible size – such as flowerpots and plants – and to understand these ordinary things we explore the worlds of the very small and very large. We delve into molecules and atoms and reach out to the stars and galaxies. Thus, we know that most atoms composing the Earth were made in stars that died long before the birth of the Sun.

This wide realm of nature, of things ranging in size from atoms to galaxies, is ruled not by the gods of antiquity, but by the laws of motion and the push and pull of electrical and gravitational forces. Electrical forces dominate on the scale of molecules and atoms, accounting for much of the intricacy of the very small; gravitational forces dominate on the scale of stars and galaxies, accounting for much of the intricacy of the very large. The exploration of this luxuriant garden of phenomena is in the care of physical sciences such as chemistry, biochemistry, geophysics, and astrophysics.

The great problems lying deep at the foundations of the physical universe are no longer found in this realm that stretches from atoms to galaxies. They are found in the outer realms of nature. When the scale of measurement decreases a hundred thousand times smaller than the size of atoms, and increases a hundred thousand times larger than the size of galaxies, we quit the lush middle realm and enter the outer realms. Here we discover the truly baffling.

The changeover from the magic universe to the mythic universe never reached completion in Australasia and other isolated lands secure from assault. The populations in these lands survived until recent times snug in their halfway magicomythic worlds. Elsewhere, the globe was in uproar with the rise of the mythic universe.

Climate changes and cultural conflicts stirred the swirl of tribal movements. Food hunters and food gatherers turned to herding and farming, and farming communities emerged between ten and twenty thousand years ago in the Middle East, India, China, Africa, Europe, and later in Mesoamerica. Tribes multiplied, merged and became nations. Powerful ruling families attained royal status, and professional priests interpreted the will of the gods. The arts burgeoned into professions and the crafts into industries. Irrigation systems connected rivers to farmlands, and large works such as Stonehenge in Britain and the pyramids in Egypt marked the rise of engineering. Trade flourished over great distances, as between the cities of Sumer and Akkadia in Mesopotamia and the far cities of Mohenjo Daro and Harappa in India.

The mythic universe was well under way more than six thousand years ago with the rise of the great gods in the delta civilizations of the Nile, Euphrates–Tigris, and Indus. “Thou art the Sole One who made all that is, the One and Only who made what existeth,” chanted the Egyptian priests of the New Kingdom in adoration of Amun the god of Thebes.

Historians would love to search the past in a Wellsian time machine and return to tell the “tales of long, long ago, long, long ago” that in the words of Thomas Bayly, a nineteenth century ballad writer, “to us are so dear.” Historians little know that a timeship has been invented by a professor in the Department of Fantasy and Virtual Reality at the University of Massachusetts. In this secret diachronic conveyance we shall take a journey – a safari in time – back to earlier periods of cosmic history.

Let me welcome you aboard with these comments. Moving backward in time is an uncommon way of presenting history, and to avoid the incongruity of a movie show in reverse, I shall occasionally stop the machine and allow time to resume its normal Newtonian flow while gazing at the scenery. I must warn you that our timeship is still in an experimental stage and will not always do exactly what we want. Please fasten your seat belts.

Tentatively I start the timeship in reverse gear and it lurches into motion. Its dials spin alarmingly, and although I slam on the brakes almost immediately, we have already traveled two million years. Through the windows we see hominids striding around in the early Pleistocene. It would be very interesting to stay and see their progress. But we have other more urgent business.