... he wanted to clear all the rubble off the site

Alberto stood up, took off the red cloak, and laid it over a chair. Then he settled himself once again in the corner of the sofa.

"Rene Descartes was born in 1596 and lived in a number of different European countries at various periods of his life. Even as a young man he had a strong desire to achieve insight into the nature of man and the universe. But after studying philosophy he became increasingly convinced of his own ignorance."

"Like Socrates?"

"More or less like him, yes. Like Socrates, he was convinced that certain knowledge is only attainable through reason. We can never trust what the old books tell us. We cannot even trust what our senses tell us."

"Plato thought that too. He believed that only reason can give us certain knowledge."

"Exactly. There is a direct line of descent from Socrates and Plato via St. Augustine to Descartes. They were all typical rationalists, convinced that reason was the only path to knowledge. After comprehensive studies, Descartes came to the conclusion that the body of knowledge handed down from the Middle Ages was not necessarily reliable. You can compare him to Socrates, who did not trust the general views he encountered in the central square of Athens. So what does one do, Sophie? Can you tell me that?"

"You begin to work out your own philosophy."

"Right! Descartes decided to travel around Europe, the way Socrates spent his life talking to people in Athens. He relates that from then on he meant to confine himself to seeking the wisdom that was to be found, either within himself or in the \'great book of the world.\' So he joined the army and went to war, which enabled him to spend periods of time in different parts of Central Europe. Later he lived for some years in Paris, but in 1629 he went to Holland, where he remained for nearly twenty years working on his mathematical and philosophic writings.

"In 1649 he was invited to Sweden by Queen Christina. But his sojourn in what he called \'the land of bears, ice, and rocks\' brought on an attack of pneumonia and he died in the winter of 1650."

"So he was only 54 when he died."

"Yes, but he was to have enormous influence on philosophy, even after his death. One can say without exaggeration that Descartes was the father of modern philosophy. Following the heady rediscovery of man and nature in the Renaissance, the need to assemble contemporary thought into one coherent philosophical system again presented itself. The first significant system-builder was Descartes, and he was followed by Spinoza and Leibniz, Locke and Berkeley, Hume and Kant."

"What do you mean by a philosophical system?"

"I mean a philosophy that is constructed from the ground up and that is concerned with finding explanations for all the central questions of philosophy. Antiquity had its great system-constructors in Plato and Aristotle. The Middle Ages had St. Thomas Aquinas, who tried to build a bridge between Aristotle\'s philosophy and Christian theology. Then came the Renais-sance, with a welter of old and new beliefs about nature and science, God and man. Not until the seventeenth century did philosophers make any attempt to assemble the new ideas into a clarified philosophical system, and the first to attempt it was Descartes. His work was the forerunner of what was to be philosophy\'s most important project in the coming generations. His main concern was with what we can know, or in other words, certain knowledge. The other great question that preoccupied him was the relationship between body and mind. Both these questions were the substance of philosophical argument for the next hundred and fifty years."

"He must have been ahead of his time."

"Ah, but the question belonged to the age. When it came to acquiring certain knowledge, many of his contemporaries voiced a total philosophic skepticism. They thought that man should accept that he knew nothing. But Descartes would not. Had he done so he would not have been a real philosopher. We can again draw a parallel with Socrates, who did not accept the skepticism of the Sophists. And it was in Descartes\'s lifetime that the new natural sciences were developing a method by which to provide certain and exact descriptions of natural processes.

"Descartes was obliged to ask himself if there was a similar certain and exact method of philosophic reflection."

"That I can understand."

"But that was only part of it. The new physics had also raised the question of the nature of matter, and thus what determines the physical processes of nature. More and more people argued in favor of a mechanistic view of nature. But the more mechanistic the physical world was seen to be, the more pressing became the question of the relationship between body and soul. Until the seventeenth century, the soul had commonly been considered as a sort of \'breath of life\' that pervaded all living creatures. The original meaning of the words \'soul\' and \'spirit\' is, in fact, \'breath\' and \'breathing.\' This is the case for almost all European languages. To Aristotle, the soul was something that was present everywhere in the organism as its \'life principle\'--and therefore could not be conceived as separate from the body. So he was able to speak of a plant soul or an animal soul. Philosophers did not introduce any radical division of soul and body until the seventeenth century. The reason was that the motions of all material objects--including the body, animal or human--were explained as involving mechanical processes. But man\'s soul could surely not be part of this body machinery, could it? What of the soul, then? An explanation was required not least of how something \'spiritual\' could start a mechanical process."

"It\'s a strange thought, actually."

"What is?"

"I decide to lift my arm--and then, well, the arm lifts itself. Or I decide to run for a bus, and the next second my legs are moving. Or I\'m thinking about something sad, and suddenly I\'m crying. So there must be some mysterious connection between body and consciousness."

"That was exactly the problem that set Descartes\'s thoughts going. Like Plato, he was convinced that there was a sharp division between \'spirit\' and \'matter.\' But as to how the mind influences the body--or the soul the body--Plato could not provide an answer."

"Neither have I, so I am looking forward to hearing what Descartes\'s theory was."

"Let us follow his own line of reasoning."

Albert pointed to the book that lay on the table between them.

"In his Discourse on Method, Descartes raises the question of the method the philosopher must use to solve a philosophical problem. Science already had its new method..."

"So you said."

"Descartes maintains that we cannot accept anything as being true unless we can clearly and distinctly perceive it. To achieve this can require the breaking down of a compound problem into as many single factors as possible. Then we can take our point of departure in the simplest idea of all. You could say that every single thought must be weighed and measured, rather in the way Galileo wanted everything to be measured and everything immeasurable to be made measurable. Descartes believed that philosophy should go from the simple to the complex. Only then would it be possible to construct a new insight. And finally it would be necessary to ensure by constant enumeration and control that nothing was left out. Then, a philosophical conclusion would be within reach."

"It sounds almost like a math test."

"Yes. Descartes was a mathematician; he is considered the father of analytical geometry, and he made important contributions to the science of algebra. Descartes wanted to use the \'mathematical method\' even for philosophizing. He set out to prove philosophical truths in the way one proves a mathematical theorem. In other words, he wanted to use exactly the same instrument that we use when we work with figures, namely, reason, since only reason can give us certainty. It is far from certain that we can rely on our senses. We have already noted Descartes\'s affinity with Plato, who also observed that mathematics and numerical ratio give us more certainty than the evidence of our senses."

"But can one solve philosophical problems that way?"

"We had better go back to Descartes\'s own reasoning. His aim is to reach certainty about the nature of life, and he starts by maintaining that at first one should doubt everything. He didn\'t want to build on sand, you see."

"No, because if the foundations give way, the whole house collapses."

"As you so neatly put it, my child. Now, Descartes did not think it reasonable to doubt everything, but he thought it was possible in principle to doubt everything. For one thing, it is by no means certain that we advance our philosophical quest by reading Plato or Aristotle. It may increase our knowledge of history but not of the world. It was important for Descartes to rid himself of all handed down, or received, learning before beginning his own philosophical construction."

"He wanted to clear all the rubble off the site before starting to build his new house ..."

"Thank you. He wanted to use only fresh new materials in order to be sure that his new thought construction would hold. But Descartes\'s doubts went even deeper. We cannot even trust what our senses tell us, he said. Maybe they are deceiving us."

"How come?"

"When we dream, we feel we are experiencing reality. What separates our waking feelings from our dream feelings?

" \'When I consider this carefully, I find not a single property which with certainty separates the waking state from the dream,\' writes Descartes. And he goes on: \'How can you be certain that your whole life is not a dream?\' "

"Jeppe thought he had only been dreaming when he had slept in the Baron\'s bed."

"And when he was lying in the Baron\'s bed, he thought his life as a poor peasant was only a dream. So in the same way, Descartes ends up doubting absolutely everything. Many philosophers before him had reached the end of the road at that very point."

"So they didn\'t get very far."

"But Descartes tried to work forward from this zero point. He doubted everything, and that was the only thing he was certain of. But now something struck him: one thing had to be true, and that was that he doubted. When he doubted, he had to be thinking, and because he was thinking, it had to be certain that he was a thinking being. Or, as he himself expressed it: Cogito, ergo sum."

"Which means?"

"I think, therefore I am."

"I\'m not surprised he realized that."

"Fair enough. But notice the intuitive certainty with which he suddenly perceives himself as a thinking being. Perhaps you now recall what Plato said, that what we grasp with our reason is more real than what we grasp with our senses. That\'s the way it was for Descartes. He perceived not only that he was a thinking /, he realized at the same time that this thinking / was more real than the material world which we perceive with our senses. And he went on. He was by no means through with his philosophical quest."

"What came next?"

"Descartes now asked himself if there was anything more he could perceive with the same intuitive certainty.

He came to the conclusion that in his mind he had a clear and distinct idea of a perfect entity. This was an idea he had always had, and it was thus self-evident to Descartes that such an idea could not possibly have come from himself. The idea of a perfect entity cannot have originated from one who was himself imperfect, he claimed. Therefore the idea of a perfect entity must have originated from that perfect entity itself, or in other words, from God. That God exists was therefore just as self-evident for Descartes as that a thinking being must exist."

"Now he was jumping to a conclusion. He was more cautious to begin with."

"You\'re right. Many people have called that his weak spot. But you say \'conclusion.\' Actually it was not a question of proof. Descartes only meant that we all possess the idea of a perfect entity, and that inherent in that idea is the fact that this perfect entity must exist. Because a perfect entity wouldn\'t be perfect if it didn\'t exist. Neither would we possess the idea of a perfect entity if there were no perfect entity. For we are imperfect, so the idea of perfection cannot come from us. According to Descartes, the idea of God is innate, it is stamped on us from birth \'like the artisan\'s mark stamped on his product.\' "

"Yes, but just because I possess the idea of a crocophant doesn\'t mean that the crocophant exists."

"Descartes would have said that it is not inherent in the concept of a crocophant that it exists. On the other hand, it is inherent in the concept of a perfect entity that such an entity exists. According to Descartes, this is just as certain as it is inherent in the idea of a circle that all points of the circle are equidistant from the center. You cannot have a circle that does not conform to this law. Nor can you ha............