"Neither a man nor a nation can live without a higher idea, and there is only one such idea on earth, that of an immortal human soul; all the other higher ideas by which men live follow from that. "

By 3000 B.C., the whole issue of life after death and the preservation of the soul had become of paramount concern for early pre-Western civilizations. In fact, with the emphasis now shifted to the individual and to the inescapable fact of personal death, these questions turned into an obsession. How else can we explain the astounding scale and extravagance of the Great Pyramid of Cheops? Built in 2720 B.C. from more than 2 million quarried limestone blocks with an average weight of two and a half tons, it soars 480 feet from the desert sands —a mighty challenge both to time and to death itself.

Central to the Egyptians' cult of the afterlife was the part played by mummification. Yet this process was so costly that it was not until the second millennium B.C. that the practice began to spread beyond the royal household. Since the pharaoh was the intermediary between the gods and the earth in a society where survival depended on organized agriculture, the cult was the key not only to social order but also to fertility. Therefore when the Egyptians connected their pharaoh's immortality with the cult of the god of vegetation, Osiris, they were symbolizing death and resurrection in the annual cycle of the very food they ate.

During the second millennium, the Osirian cult gained in strength, and people's views on the afterlife tended to change. While mummification implied physical immortality for the body in this world, Osiris came to be thought of as the ruler of the dead in another realm. So, increasingly, the soul was thought of as having a separate existence from the body.

According to Egyptian theology a person had not just one but two or more souls, different in nature from each other. Principally, there was the ka, or "guardian spirit," shown in tomb paintings as hovering over the mummy in the guise of a small bird with a human face. And there was the ka, or "breath," which gave animation to the body. Both the ka and the ba

were thought to leave the body at death—but only temporarily. In the strange ceremony known as the Opening of the Mouth, the mouth and eyes of the corpse were pried open by means of special instruments held by a priest. This supposedly allowed the breath soul back into the mummy and commemorated the myth that Osiris, after the god Seth had killed and dismembered him, was brought back to life in the same way by his son Horus. With the ka restored to its rightful owner, it was left only for the ka to fly back and reunite with its companion. This was thought to take place in a second, parallel ceremony in the next world. Recognition of the body by the ka being all- important, it was essential for the dead person's appearance to be faithfully preserved by embalming.

Mummification and its attendant ceremonies helped ensure reunion between body and soul in the hereafter. But even with these precautions, the dead king was not guaranteed immortality. For this he still needed the compliance of the major deities. Once inside the spirit world, the deceased would be led by the jackal-headed god, Anubis, to the judgment scales, where his heart would be weighed against a feather symbolizing Maat, the goddess of justice and truth. If the scales balanced, Osiris would rule that the man had led a blameless life and so deserved to be made immortal. Conversely, if his heart proved too heavy, a less attractive fate lay in store: the unfortunate sinner would be fed to the permanently ravenous dog-monster Amemait, which lurked nearby.

For those today who believe in an afterlife, there is a tendency to link the notion of life after death with that of a particular god. But theology and conjectures about the human soul have not always gone hand in hand. In ancient Greece, where many people eventually grew tired of the all-too-human antics of Zeus and his cronies, philosophers started to argue about the nature of the soul from a purely academic and secular point of view. Their approach was to travel about, look at the world in a detached, almost arrogant sort of way, and then theorize. The word theory, in fact, comes from the Greek for "sight-seeing."

Pythagoras, in the late sixth century B.C., was the first to establish an entire school of thought based on this method of inquiry. He was struck especially by the way that the physical world seemed to be underpinned by relationships between pure numbers. Nature, apparently, had a mathematical infrastructure. At the same time, Pythagoras pointed out that mathematical entities are somehow subtler than their counterparts in the "real" world of the senses. A circle drawn in the sand may seem from a distance to be exactly circular but, on closer inspection, always turns out to have little bumps and dimples. A mathematical circle, on the other hand, is perfect in every way and can therefore only be pictured in the mind. From this line of thinking stemmed the theory of ideas (idea is Greek for "picture"), or Forms, which was developed by Socrates, Plato and others.

Pythagoras was both a mathematician and an incurable mystic. Among his many discoveries, he found that harmonious notes on a vibrating string always occur at lengths that are in simple numerical ratios to the fundamental (that is, the note made by the open vibrating string). To others this may have seemed a mere curiosity, a pleasing coincidence of nature. But to Pythagoras it was the expression of a deep mystical truth. From it, he concluded that the soul was an attunement of the body. A properly balanced body will carry a harmonious soul, just as a properly tuned string will emit a harmonious sound.

Socrates (c. 470-399 B.C.) took a different line. His theory of the soul had its roots in an earlier Pythagorean doctrine that there are three ways of life. This was exemplified by the three kinds of men who attended the Pythian games at Delphi: the athletes, the spectators and those who bought and sold. By analogy, Socrates argued that the soul has, in descending order, a rational part, an emotional part and an acquisitive part. In the just soul these are properly ordered, each minding its own business and obeying the parts ranked above. Reason, at the top, rules emotion. Emotion, in turn, helps to inspire the actions that reason dictates.

Because the just soul is ruled by reason, Socrates linked it to the realm of Forms. A Form was held to be a perfect, unchanging counterpart of something real. Socrates taught that a "particular," for example a cup, is what it is by virtue of participating in the Form, or picture, of the cup—the constant and unique prototype of cups that exists in the realm of ideas. The point is echoed in the way we use language: there are many cups of many shapes, sizes, textures and colors, but there is only one word cup, which we use to refer to them all. Though a cup might break, the Form remains intact, as does the word.

The realm of Forms was believed to have a definite structure and hierarchy. At the top was the Form of the Good, under which all other Forms were arranged. From this, Socrates deduced that the knowledgeable soul is bound to be good; its existence will consist in contemplating the Form of the Good. Evil, therefore, springs from ignorance, which arises when the soul is ruled by the body. Since the good soul is connected to the Forms, whereas the body belongs to the world of particulars, the soul lasts but the body does not.

Unfortunately, Socrates' conjectures about the nature of the soul scarcely outlived the man himself— thanks to Plato. Having originally championed the theory of Forms, Plato (c. 427-347 B.C.) went on to demolish it completely in a dialogue called the Parmenides. The setting is a meeting between the philosophers Socrates, Parmenides, and Zeno, in Athens, in about 450 B.C. By then, Parmenides, one of the fathers of Greek philosophy, was an old man, his disciple Zeno was at the height of his powers, and Socrates was young and (conveniently for Plato) still somewhat inexperienced. In the dialogue, Parmenides points out that the Forms fail to account for what we see because there is no way of linking them with particulars. The fink would have to be either another Form or another particular, and therefore would itself have to be linked, and so on forever without resolution.

Having thus logically disposed of Forms, Plato went on to develop his idea of the soul as a prime mover. In other words, the soul is what produces motion, both of itself and of other objects. Since this happens only in living things, it must be their basic principle, so that the soul comes

before the body and the feelings of the soul before the material qualities of the body. Ethical qualities —those that determine conduct—therefore spring from the soul. This holds not only for positive ethical qualities but also for their opposites; evil, as much as good, has its origins in the soul.

With Aristotle (384-322 B.C.) the basis for speculation at last shifted away from pure theory to biological observation. Aristotle was not exactly a scientist in the modern sense because he never went to the trouble of testing his ideas by experiment But he was undoubtedly a great observer and encyclopedist From his studies of fauna and flora he, like Socrates, saw the need for three different types of soul—in his case known as the nutritive, the sensitive and the rational. All living things require nourishment, so plants, animals and men alike must have a nutritive soul. Animals and men have both nutritive and sensitive functions. But man alone is rational. The Aristotelean relation between body and soul is the same as that between matter and form. The soul makes a man what he is but has no existence independent of the body. It is like a hallmark stamped on a bar of metal. When the body disintegrates, so does the soul. Only the rational function is not completely lost. It goes back to where it came from—a kind of reservoir of rationality, a common sea of intellectual consciousness.

Personal gods find no special place in the philosophies of Pythagoras, Socrates, Plato and Aristotle. Yet there are clear implications for morality. Socrates considered that a good life was one spent in the pursuit of the Form of the Good. For Aristotle, goodness was directly linked with the proper and consistent use of reason— always choosing the appropriate middle ground between extremes of action. The good soul is balanced, harmonious and, above all, rational.

Strange as it may seem now, the great thinkers of the Golden Age in Greece had very confused views about the role of the brain. Aristotle, the most influential of them all, never considered the brain to be a possible seat of the soul or of the mind. He believed it was just a cooling system, filled with phlegm —the mucus of a runny nose offering proof. Thought, intellect and the soul, he maintained, resided in the heart—a belief we still whimsically recall today with our "heartfelt" emotions and, symbolically, with a heart-shaped love sign. (The Egyptians also held this view, which is why they discarded the brain yet preserved or substituted the heart so that it could be weighed before Osiris on the judgment scales.)

It was only in the second century A D. that the Greek-born physician Galen (c. 130-200 A.D.) pointed indisputably to the brain as the site of mental activity. Galen, who rose to fame after his successful treatment of

the Roman emperor Marcus Aurelius, would publicly dissect the nerves in the neck of a live pig. As these were severed, one by one, the pig would continue to squeal; however, when Galen cut one of the laryngeal nerves (now also known as "Galen's nerves"), the squealing abruptly stopped, to the awe of the crowd. In this gruesome manner, Galen showed beyond doubt that it was the brain, via a network of nerves, that was in charge of the rest of the body.

Although disagreeing with Aristotle on the role of the brain,

Galen did accept Aristotle's theory of the tripartite soul—indeed, he embellished it. To the three basic elements, he added imagination and memory, as well as all motor and sensory functions. Later, the Roman Catholic Church appropriated Galen's ideas (along with many other off-the-shelf classical views about the universe), even going so far as to suggest specific sites in the brain where the various functions of the soul might reside. And there the matter lay. For more than a thousand years, no one cared to hazard an alternative theory, such was the all-pervasive and intimidating power of the Church in Europe.

Then came the Renaissance and, with it, the renewal of the spirit of inquiry. Giordano Bruno, an outspoken Dominican monk, was burned at the stake. Galileo was threatened with torture. But the tidal wave of new ideas was unstoppable and soon the Church was forced to abandon its long-held grip on the material cosmos.

According to Frenchman Rene Descartes (1596-1650), there were two radically different kinds of stuff in the universe. The first, consisting of physical, or extended, substance (res extensa), has length, breadth and depth, and can therefore be measured and divided. The second, or purely mental substance (res cogitans), is both intangible and indivisible. The outside world, including the human body, belongs to the first category, while the internal world of the mind belongs to the second.

These new, clear-cut distinctions between primary and secondary qualities, matter and mind, objective and subjective, had the effect of excluding human consciousness from the scientific picture of the world. Insofar as man was now anything at all, he was a biological machine. The only remaining point to debate was whether, connected in some way with this flesh-and-blood machine, there was an immaterial spirit or soul.

Descartes had very definite ideas about this. Having received the best education his time could offer, Descartes rejected most of the Scholastic dogma served up by his Jesuit teachers and set out to rebuild knowledge on what he considered a firmer basis. His efforts led him to become one of the recognized founders of modern philosophy.

In the synopsis of his Meditations on First Philosophy, published in 1641, Descartes wrote:

What have said is sufficient to show clearly enough that the extinction of the mind does not follow from the corruption of the body, and also to give men the hope of another life after death. "

It hardly seems like a revolutionary idea. After all, Descartes' "dualism,"," or theory of two substances, has some obvious features in common with the Church's traditional view of the body and the soul. But Descartes broke sharply with religious orthodoxy in at least one very important respect —his belief that logic could unlock the secrets of the soul.

Philosophers of all persuasions now joined in the debate, unfettered (if not entirely uninfluenced) by the teachings of the Church. Do we, as Descartes maintained, have a soul that is distinct and separate from the brain? If so, then corporeal death may not be the end but simply a phase transition, a metamorphic event in which we break free of materiality as a prelude to moving on. Or, are the soul and the mind truly ephemeral— artifacts of the living brain, doomed to die when the brain dies?

One of the dualist's main problems is to come up with a mechanism— any mechanism—by which the soul and the brain can interact. This is like Plato's dilemma in trying to link Forms with particulars. It is the actual coupling that is the tricky aspect. If the soul is immaterial and the brain is made of ordinary matter, then how can the two possibly establish contact and influence each other?

The English philosopher John Locke (1632-1704) pondered long and hard over the dualism issue and was not convinced by Descartes's explanation of how the soul and the brain communicate. Perhaps, he argued, mind is material and God endows matter, in man's case, with the power to think and know.

Locke remained a dualist—just. But not so his compatriot Thomas Hobbes (1588-1679). Hobbes was an out-and-out determinist, a man who had been powerfully influenced in his youth by the new "mechanical philosophy" of Galileo. All things to Hobbes could be explained as if they were machines. To him, the soul was no more than the thinking body. It is a sentiment that has been echoed many times since, most memorably in 1949 by the English philosopher Gilbert Ryle, who derided Descartes's notion of the mind as a "ghost in the machine."

Has that ghost finally been exorcised by scientific reductionism? Among the ranks of biologists and philosophers today, there is no doubt that materialists hold sway. The brain is under the microscope as never before, and the hope of many researchers seems to be that all of its functions—all that our minds are capable of—will someday be understandable in purely physical terms.

And yet, the voice of the dissidents is insistent and perhaps, once again, becoming hard to ignore. As Lewis Thomas, the distinguished cancer research administrator and writer, eloquently put it:

There is still that permanent vanishing of consciousness to be accounted for. Are we to be stuck forever with this problem? Where on Earth does it go? Is it simply stopped dead in its tracks, lost in humus, wasted? Considering the tendency of nature to find uses for complex and intricate mechanisms, this seems to me unnatural I prefer to think of it somehow as separated off at the filaments of its attachment and then drawn like an easy breath back into the membrane of its origin a fresh memory for a biospherical nervous . . .

The great question remains, after millennia of debate: can mind survive in some form without its neural hardware—and, if so, in what form? Is mind just our subjective experience of the brain at work or do mind and brain have a separate, parallel existence?

Reprinted with permission. @ 1995 Random House., Inc., NY, NY.

David Darling Ph.D. received his doctorate from Cambridge and has written for Astronomy magazine.

As physics is presently constituted, an attribute called consciousness will not appear in the mathematical formalisms. The reason, of course, is that consciousness has not been introduced as a property possessed by a quantum system such as an electron. Let me explain this with an analogy. The concept of charge was introduced because bodies seemed to exert forces on one another in certain circumstances. Once charge was formally recognized and defined, the whole theory of electromagnetism followed. For consciousness to enter physics, a similar procedure might have to be used. But in order do this physicists would have to admit that consciousness exists and can be assigned attributes. Quantum theory does seem to indicate that consciousness is an attribute of a quantum system. Very simply quantum theory is described by two equations. One is a deterministic wave equation and the second is a probability equation. Amazingly, the two equations are connected only by an act of observation. Observation implies consciousness, at least to some physicists. So there is an indication that consciousness will have to be treated in physics.