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The Beginning of Modern Science
E pur si muove -- And yet it moves. Galileo Galilei, sotto voce after his trial.
One thing that happened during the Renaissance that was of great importance for the later character of modern philosophy was the birth of modern science. Even as in the Middle Ages philosophy was often thought of as the "handmaiden of theology," modern philosophers have often thought of their discipline as little more than the "handmaiden of science." Even for those who haven't thought that, the shadow of science, its spectacular success and its influence on modern life and history, has been hard to ignore.
For a long time, philosophers as diverse as David Hume, Karl Marx, and Edmund Husserl have seen the value of their in work in the claim that they were making philosophy "scientific." Those claims should have ended with Immanuel Kant (1724-1804), who for the first time clearly provided a distinction between the issues that science could deal with and those that it couldn't, but since Kant's theory could not be demonstrated the same way as a scientific theory, the spell of science, even if it is only through pseudo-science, continues.
The word "science" itself is simply the Latin word for knowledge: scientia. Until the 1840's what we now call science was "natural philosophy," so that even Isaac Newton's great book on motion and gravity, published in 1687, was The Mathematical Principles of Natural Philosophy (Principia Mathematica Philosophiae Naturalis). Newton was, to himself and his contemporaries, a "philosopher." In a letter to the English chemist Joseph Priestley written in 1800, Thomas Jefferson lists the "sciences" that interest him as, "botany, chemistry, zoology, anatomy, surgery, medicine, natural philosophy [this probably means physics], agriculture, mathematics, astronomy, geography, politics, commerce, history, ethics, law, arts, fine arts." The list begins on familiar enough terms, but we hardly think of history, ethics, or the fine arts as "sciences" any more. Jefferson simply uses to the term to mean "disciplines of knowledge."
Something new was happening in natural philosophy, however, and it was called the nova scientia, the "new" knowledge. It began with Mikolaj Kopernik (1473-1543), 
whose Polish name was Latinized to Nicolaus Copernicus. To ancient and mediaeval astronomers the only acceptable theory about the universe came to be that of geocentrism, that the Earth is the center of the universe, with the sun, moon, planets, and stars moving around it. But astronomers needed to explain a couple of things: why Mercury and Venus never moved very far away from the sun -- they are only visible a short time after sunset or before sunrise -- and why Mars, Jupiter, and Saturn sometimes stop and move backwards for a while (retrograde motion) before resuming their forward motion. Believing that the heavens were perfect, everyone wanted motion there to be regular, uniform, and circular. The system of explaining the motion of the heavenly bodies using uniform and circular orbits was perfected by Claudius Ptolemy, who lived in Egypt probably during the reign of the Emperor Marcus Aurelius (161-180). His book, still known by its Arabic title, the Almagest (from Greek Tò Mégiston, "The Greatest"), explains that the planets are fixed to small circular orbits (epicycles) which themselves are fixed to the main orbits. With the epicycles moving one way and the main orbits the other, the right combination of orbits and speeds can reproduce the motion of the planets as we see them. The only problem is that the system is complicated. It takes something like 27 orbits and epicycles to explain the motion of five planets, the sun, and the moon. This is called the Ptolemaic system of astronomy.
Copernicus noticed that it would make things a lot simpler (Ockham's Razor) if the sun were the center of motion rather than the earth. The peculiarities of Mercury and Venus, not explained by Ptolemy, now are explained by the circumstance that the entire orbits of Mercury and Venus are inside the Earth's orbit. They cannot get around behind the Earth to be seen in the night sky. The motion of Mars and the other planets is explained by the circumstance that the inner planets move faster than the outer ones. Mars does not move backwards; it is simply overtaken and passed by the Earth, which makes it look, against the background, as though Mars is moving backwards. Similarly, although it looks like the stars move once around the Earth every day, Copernicus figured that it was just the Earth that was spinning, not the stars. This was the Copernican Revolution.
Now this all seems obvious. But in Copernicus's day the weight of the evidence was against him. The only evidence he had was that his system was simpler. Against him was the prevailing theory of motion. Mediaeval physics believed that motion was caused by an "impetus." Things are naturally at rest. An impetus makes something move; but then it runs out, leaving the object to slow down and stop. Something that continues moving therefore has to keep being pushed, and pushing is something you can feel. (This was even an argument for the existence of God, since something very big -- like God -- had to be pushing to keep the heavens going.) So if the Earth is moving, why don't we feel it? Copernicus could not answer that question. Neither was there an obvious way out of what was actually a brilliant prediction: If the stars did not move, then they could be different distances from the earth; and as the earth moved in its orbit, the nearer stars should appear to move back and forth against more distant stars. This is called "stellar parallax," but unfortunately stellar parallax is so small that it was not observed until 1838. So, at the time, supporters of Copernicus could only contend, lamely, that the stars must all be so distant that their parallax could not be detected. Yeah, sure. In fact, the absence of parallax had been used since the Greeks as more evidence that the Earth was not moving.
It is common now in many venues for people to say that heliocentric astronomy was rejected by the Greeks and ignored in the Middle Ages just because of the human arrogance that wanted the Earth to be the center of the universe -- we belong in the center of things. There were certainly some people who thought that way, but it is hard to imagine that all Greeks, or all Mediaevals, were so foolish. They weren't. The little morality tale we are given of Mediaeval ignorance and anthropo-centrism overlooks the problem that there was no evidence of heliocentrism in Ancient or Mediaeval science, that Copernicus himself did not supply any evidence, and that it was the Ancient and Mediaeval understanding of the physics that was dead against the Earth moving. Usually these treatments don't even mention the physics. The only evidence that Stephen Hawking mentions against Ptolemaic astronomy (in his A Brief History of Time) at the end of the Middle Ages is that the Moon, moving on an epicycle, would move away from and towards us in a way that would dramatically change its apparent size. Unfortunately, Copernicus retained an epicycle for the motions of the Moon, which means that this problem with Ptolemaic astronomy is equally a problem for Copernican astronomy. Only Johannes Kepler (1571-1630) would fix things by replacing epicycles with elliptical orbits. That Copernicus supplied no compelling evidence for this theory led Thomas Kuhn to think that Copernicanism won out only because of social, not evidentiary, factors. But then Copernicanism did not triumph until Galileo, and the evidentiary situation with Galileo was much different than it had been with Copernicus.
Copernicus was also worried about getting in trouble with the Church. The Protestant Reformation had started in 1517, and the Catholic Church was not in any mood to have any more of its doctrines, even about astronomy, questioned. So Copernicus did not let his book be published until he lay dying.
The answers, the evidence, and the trouble for Copernicus's system came with Galileo Galilei (1564-1642). Galileo is important and famous for three things:
Most importantly he applied mathematics to motion. This was the real beginning of modern science. There is no math in Aristotle's Physics. There is nothing but math in modern physics books. Galileo made the change. It is inconceivable now that science could be done any other way. Aristotle had said, simply based on reason, that if one object is heavier than another, it will fall faster. Galileo tried that out (though it had already been done by John Philoponus in the 6th century) and discovered that Aristotle was wrong. Aerodynamics aside, everything falls at the same rate. But then Galileo determined what that rate was by rolling balls down an inclined plane (not by dropping them off the Leaning Tower of Pisa, which is the legend). This required him to distinguish between velocity (e.g. meters per second) and acceleration (change in velocity, e.g. meters per second per second). Gravity produced an acceleration -- 9.8 meters per second per second. Instantly Galileo had an answer for Copernicus: simple velocity is not felt, only acceleration is. So the earth can be moving without our feeling it. Also, velocity does not change until a force changes it. That is the idea of inertia, which then replaced the old idea of an impetus. All this theory was ultimately perfected by Isaac Newton (1642-1727).
With the objections to Copernicus's theory removed, the case was completed with positive evidence. Around 1609 it was discovered in the Netherlands that putting two lenses (which had been used since the 13th century as eye glasses) together made distant objects look close. Galileo heard about this and himself produced the first astronomical quality telescope. With his telescope he saw several things: a) the Moon had mountains and valleys. This upset the ancient notion that the heavens, the Moon included, were completely unlike the Earth. b) the Planets all showed disks and were not points of light like stars. c) Jupiter had four moons. This upset the argument, which had been used against Copernicus, that there could only be one center of motion in the universe. Now there were three (the Sun, Earth, and Jupiter). d) There were many more stars in the sky than could be seen with the eye; and the Milky Way, which always was just a glow, was itself composed of stars. And finally e) Venus went through phases like the Moon. 
That vindicated Copernicus, for in the Ptolemaic system Venus, moving back and forth at the same distance between the Earth and the Sun, would only go from crescent to crescent. It would mostly have its dark side turned to us. With Copernicus, however, Venus goes around on the other side of the Sun and so, in the distance, would show us a small full face. As it comes around the Sun towards the Earth (in the evening sky), we would see it turn into a crescent as the disk grows larger. Those are the phases, from small full to large crescent, that Galileo saw. So that he could claim priority to this discovery, before actually announcing it, Galileo concealed his claim in an anagram that unscrambled to Cynthiae figuras aemulatur mater amorum, "The forms of Cynthia [the moon], the mother of loves imitates." The only argument that could be used against Galileo for all these discoveries was that the telescope must be creating illusions. In fact it was not well understood why a telescope worked. Some people looked at stars and saw two instead of one. That seemed to prove that the telescope was unreliable. Soon it was simply accepted that many stars are double. They still are.- With his evidence and his arguments, Galileo was ready to prove the case for Copernican astronomy. He had the support of the greatest living astronomer, Johannes Kepler, but not the Catholic Church. He had been warned once to watch it, but then a friend of his (Maffeo Barberini) became Pope Urban VIII (1623-1644). The Pope agreed that Galileo could write about both Ptolemaic and Copernican systems, setting out the arguments for each. Galileo wrote A Dialogue on the Two Principal Systems of the World (1632). Unfortunately, the representative of the Ptolemaic system in the dialogue was made to appear foolish, and the Pope thought it was a caricature of himself. Galileo was led before the Inquisition, "shown the instruments of torture," and invited to recant. He did, but was kept under house arrest for the rest of his life. Nevertheless, it was too late. No serious astronomer could ever be a geocentrist again, and the only discredit fell against the Church. As Galileo left his trial, he is supposed to have muttered, E pur si muove -- "And yet it moves."
Some think less of Galileo because he recanted his beliefs, while Socrates was willing to die for his. Well, there has been no more civilized example of a death penalty than when Socrates got to sit around, talk to his friends, calmly drink the hemlock, and lie down to a peaceful death -- the "sweet shafts," the agana belea, of Apollo's silent arrows. Galileo was threatened with torture. No one can be faulted for saying anything under those circumstances.
Indeed, the history of science subsequently often consists of who gets to claim the status of Galilean martyrdom. The interesting cases in our day concern Global Warming and Evolution. The weight of Offical Science -- journals like Nature, the National Science Foundation, or the Royal Society of Britain -- is all for Global Warming and for Evolution. The Right complains that multiple equivalents of Galileo are oppressed because they stand up for the heretical truth, that Global Warming and Evolution are frauds. Unfortunately, this confuses very different issues. Evolution is in no danger from any real science; and the Right wastes a great deal of money and effort (such as Ben Stein's movie Expelled) promoting theology and bad metaphysics as some sort of "science." On the other hand, the Global Warming "consensus" is a product of politics, not science. The Right thus plays right into the hands of Al Gore, who is happy to lump "Intelligent Design" and Global Warming skepticism as equally part of an "assault on reason." This when a great deal of enthusiasm for the Global Warming cause follows from hostility to science itself, in so far as it represents human progress and the betterment of human life on earth. Thus, between the Earth Liberation Front and the Creationists (not to mention Post-Modernist nihilism), there is little real interest in the modern tradition of science begun by Copernicus and Galileo.
Copyright (c) 1996, 1998, 2006, 2008 Kelley L. Ross, Ph.D. All Rights Reserved
René Descartes (1596-1650) and the Meditations on First Philosophy
Descartes is justly regarded as the Father of Modern Philosophy. This is not because of the positive results of his investigations, which were few, but because of the questions that he raised and problems that he created, problems that have still not been answered to everyone's satisfaction: particularly the Problem of Knowledge and the Mind-Body Problem. And in a day when philosophy and science were not distinguished from each other, Descartes was a famous physicist and mathematician as well as a philosopher. Descartes' physics was completely overthrown by that of Newton, so we do not much remember him for that. But Descartes was a great mathematician of enduring importance. He originated analytic geometry, where all of algebra can be given geometrical expression. Like Galileo combining physics and mathematics, this also combined two things that had previously been apart, arithmetic and geometry. The modern world would not be the same without graphs of equations. Rectangular coordinates for graphing are still called Cartesian coordinates (from Descartes' name: des Cartes). Descartes is also the person who began calling the square root of -1 (i.e. 
-1) the "imaginary" number. Descartes lived in an age of great mathematicians, including Marin Mersenne (1588-1648), Pierre Fermat (1601-1665), Blaise Pascal (1623-1662), and Christian Huygens (1629-1695). At a time before scientific journals, Mersenne himself mediated a correspondence between all these people (as well as with Galileo, Thomas Hobbes, and many others). All prime numbers that are powers of 2 minus 1 (i.e. 2n - 1) are still called "Mersenne primes." Huygens then lived long enough to know Isaac Newton (1642-1727).
Seeing Descartes as a mathematician explains why he was the kind of philosopher that he was. Now it is hard to reconcile Descartes' status as a scientist and the inspiration he derived from Galileo and others with his clear distrust of experience. Isn't science about experience? We might think so. But the paradox of modern science is its dependence on mathematics. Where does mathematics come from? What makes it true? Many mathematicians will still answer that they are "Platonists," but Plato's views certainly have little to do with experience. So Descartes belongs to this puzzling, mathematical side of science, not to the side concerned with experience.
Meditations on First Philosophy is representative of his thought. "First philosophy" simply means what is done first in philosophy. The most important thing about Descartes as a philosopher is that "first philosophy" changed because of what he did. What stood first in philosophy since Aristotle was metaphysics. Thus the first question for philosophy to answer was about what is real. That decided, everything else could be done. With such an arrangement we can say that philosophy functions with Ontological Priority. In the Meditations we find that questions about knowledge come to the fore. If there are problems about what we can know, then we may not even be able to know what is real. But if questions about knowledge must be settled first, then this establishes Epistemological Priority for philosophy. Indeed, this leads to the creation of the Theory of Knowledge, Epistemology, as a separate discipline within philosophy for the first time. Previously, knowledge had been treated as falling in the domain of Aristotle's logical works (called, as a whole, the Organon), especially the Posterior Analytics. Modern philosophy has been driven by questions about knowledge. It begins with two principal traditions, Continental Rationalism and British Empiricism. The Rationalists, including Descartes, believed that reason was the fundamental source of knowledge. The Empiricists believed that experience was. Epistemological priority makes possible what has become a very common phenomenon in modern philosophy: denying that metaphysics is possible at all, or even that metaphysical questions mean anything. That can happen when epistemology draws the limits of knowledge, or the limits of meaning, so tight that metaphysical statements or questions are no longer allowed.
The most important issues get raised in the first three of the six Meditations. In the first meditation Descartes begins to consider what he can know. He applies the special method that he has conceived (about which he had already written the Discourse on Method), known as "methodical doubt." As applied, methodical doubt has two steps: 1) doubt everything that can be doubted, and 2) don't accept anything as known unless it can be established with absolute certainty. Today Descartes is often faulted for requiring certainty of knowledge. But that was no innovation with him: ever since Plato and Aristotle, knowledge was taken to imply certainty. Anything without certainty would just be opinion, not knowledge. The disenchantment with certainty today has occurred just because it turned out to be so difficult to justify certainty to the rigor that Descartes required. Logically the two parts of methodical doubt are very similar, but in the Meditations they are procedurally different. Doubt does its job in the first meditation. Descartes wonders what he can really know about a piece of matter like a lump of wax. He wonders if he might actually be dreaming instead of sitting by the fireplace. Ultimately he wonders if the God he has always believed in might actually be a malevolent Demon capable of using his omnipotence to deceive us even about our own thoughts or our own existence. Thus, there is nothing in all his experience and knowledge that Descartes cannot call into doubt. The junk of history, all the things he ever thought he had known, gets swept away.
Ever since the Meditations, Descartes' Deceiving Demon has tended to strike people as a funny or absurd idea. Nevertheless, something far deeper and more significant is going on in the first meditation than we might think. It is a problem about the relation of causality to knowledge. The relation of cause to effect had been of interest since Aristotle. There was something odd about it. Given knowledge of a cause (and of the laws of nature), we usually can predict what the effect will be. Touch the hot stove, and you'll get burned. Step off a roof, and you'll fall. But given the effect, it is much more difficult to reason backwards to the cause. The arson squad shows up to investigate the cause of a fire, but that is not an easy task: many things could have caused the fire, and it is always possible that they might not be able to figure out at all what the cause was. The problem is that the relation between cause and effect is not symmetrical. Given a cause, there will be one effect. But given an effect, there could have been many causes able to produce the same effect. And even if we can't predict the effect from the cause, we can always wait around to see what it is. But if we can't determine the cause from the effect, time forever conceals it from us. This feature of causality made for some uneasiness in mediaeval Western, and even in Indian, philosophy. Many people tried to argue that the effect was contained in the cause, or the cause in the effect. None of that worked, or even made much sense.
With Descartes, this uneasiness about causality becomes a terror in relation to knowledge: for, in perception, what is the relation of the objects of knowledge to our knowledge of them? Cause to effect. Thus what we possess, our perceptions, are the effects of external causes; and in thinking that we know external objects, we are reasoning backwards from effect to cause. Trouble. Why couldn't our perceptions have been caused by something else? Indeed, in ordinary life we know that they can be. There are hallucinations. Hallucinations can be caused by a lot of things: fever, insanity, sensory deprivation, drugs, trauma, etc. Descartes' Deceiving Demon is more outlandish, but it employs the same principle, and touches the same raw nerve. That raw nerve is now known as the Problem of Knowledge: How can we have knowledge through perception of external objects? There is no consensus on how to solve this even today. The worst thing is not that there haven't been credible solutions proposed, there have been, but that the solutions should explain why perception is so obvious in ordinary life. Philosophical explanations are usually anything but obvious; but no sensible person, not even Descartes, really doubts that external objects are there. This is why modern philosophy became so centered on questions about knowledge: it is the Curse of Descartes.
In his own discussion, Descartes does not identify his problem as resulting from the asymmetry of cause and effect as applied to knowledge. However, this is what underlies his difficulty, and an explicit statement of the matter does not have long to wait. In 1690, Bishop Pierre-Daniel Huet, a member of the French Academy, wrote that any event can have an infinite number of possible causes. Huet was certainly aware of Descartes' work (as any Frenchman by then would have been), and certainly took his epistemological difficulties seriously. Indeed, Huet's book was a celebration of epistemological difficulties, entitled a Philosophical Treatise on the Weaknesses of the Human Mind. We also get an interesting but confused discussion of the asymmetry of cause and effect in the Sherlock Holmes stories.
In the second meditation, Descartes wants to begin building up knowledge from the wreckage of the first meditation. This means starting from nothing. Such an idea of building up knowledge from nothing is called Foundationalism and is one of the mistakes that Descartes makes. Descartes does not and cannot simply start from nothing. Nevertheless, he gets off to a pretty good start: he decides that he cannot be deceived about his own existence, because if he didn't exist, he wouldn't be around to worry about it. If he didn't exist, he wouldn't be thinking; so if he is thinking, he must exist. This is usually stated in Latin: Cogito ergo sum, "I think therefore I am." That might be the most famous statement in the history of philosophy, although it does not seem to occur in that form in the Meditations.
But there is more to it than just Descartes' argument for his own existence. Thinking comes first, and for Descartes that is a real priority. The title of the second meditation actually says, "the mind is better known than the body," and the cogito ergo sum makes Descartes believe, not just that he has proven his existence, but that he has proven his existence as a thinking substance, a mind, leaving the body as some foreign thing to worry about later. That does not really follow, but Descartes clearly thinks that it does and consequently doesn't otherwise provide any special separate proof for the existence of the soul. In the end Descartes will believe that there are two fundamental substances in the world, souls and matter. The essence of soul for him, the attribute that makes a soul what is it, is thinking. The essence of matter for him (given to us in the fifth meditation), the attribute that makes matter what is it, is extension, i.e. that matter takes up space. This is known as Cartesian Dualism, that there are two kinds of things. It is something else that people have thought funny or absurd since Descartes. The great difficulty with it was always how souls and their bodies, made of matter, interact or communicate with one another. In Descartes' own physics, forces are transferred by contact; but the soul, which is unextended and so has no surface (only matter has extension), cannot contact the body because there is no surface to press with. The body cannot even hold the soul within it, since the soul has nothing to press upon to carry it along with the body. Problems like this occur whenever the body and soul are regarded as fundamentally different kinds of realities.
Today it might seem easy to say that the body and soul communicate by passing energy back and forth, which doesn't require contact, or even proximity; but the presence of real energy in the soul would make it detectable in the laboratory: any kind of energy produces some heat (towards which all energy migrates as it becomes more random, i.e. as energy obeys the laws of the conservation of energy and of entropy), and heat or the radiation it produces (all heat produces electromagnetic radiation) can be detected. But, usually, a theory of the soul wants it to be some kind of thing that cannot be detected in a laboratory -- in great measure because souls have not been detected in a laboratory.
Nevertheless, Descartes' problem is not just a confusion or a superstition. Our existence really does seem different from the inside than from the outside. From the inside there is consciousness, experience, colors, music, memories, etc. From the outside there is just the brain: gray goo. How do those two go together? That is the enduring question from Descartes: The Mind-Body Problem. As with the Problem of Knowledge, there is no consensus on a satisfactory answer. To ignore consciousness, as happens in Behaviorism, or to dismiss consciousness as something that is merely a transient state of the material brain, is a kind of reductionism, i.e. to say the one thing is just a state or function of another even though they may seem fundamentally different and there may be no good reason why we should regard that one thing as more real and the other less so. Much of the talk about the Mind-Body Problem in the 20th century has been reductionistic, starting with Gilbert Ryle's Concept of Mind, which said that "mind is to body as kick is to leg." A kick certainly doesn't have much reality apart from a leg, but that really doesn't capture the relationship of consciousness to the body or to the brain. When the leg is kicking, we see the leg. But when the brain is "minding," we don't see the brain, and the body itself is only represented within consciousness. Internally, there is no reason to believe the mind is even in the brain. Aristotle and the Egyptians thought that consciousness was in the heart. In the middle of dreaming or hallucinations, we might not be aware of our bodies at all.
At the end of the second mediation Descartes may reasonably be said to have proven his own existence, but the existence of the body or of any other external objects is left hanging. If nothing further can be proven, then each of us is threatened with the possibility that I am the only thing that exists. This is called solipsism, from Latin solus, "alone" (sole), and ipse, "self." Solipsism is not argued, advocated, or even mentioned by Descartes, but it is associated with him because both he and everyone after him have so much trouble proving that something else does exist.
The third meditation is Descartes' next step in trying to restore the common sense limits of knowledge. Even though he is ultimately aiming to show that external objects and the body exist, he is not able to go at that directly. Instead the third meditation is where Descartes attempts to prove the existence of God. This is surprising, since the existence of objects seems much more obvious than the existence of God; but Descartes, working with his mathematician's frame of mind, thinks that a pure rational proof of something he can't see is better than no proof of something he can.
Descartes' proof for God is not original. It is a kind of argument called the Ontological Argument (named that by Immanuel Kant, 1724-1804). It is called "ontological" because it is based on an idea about the nature of God's existence: that God is a necessary being, i.e. it is impossible for him not to exist. We and everything else in the universe, on the other hand, are contingent beings; it is possible for us not to exist, and in the past (and possibly in the future) we have indeed not existed. But if God is a necessary being, then there must be something about his nature that necessitates his existence. Reflecting on this, a mediaeval Archbishop of Canterbury, St. Anselm (1093-1109), decided that all we needed to prove the existence of God was the proper definition of God. With such a definition we could understand how God's nature necessitates his existence. The definition Anselm proposed was: God is that than which no greater can be conceived. The argument then follows: If we conceive of a non-existing God, we must always ask, "Can something greater than this be conceived?" The answer will clearly be "Yes"; for an existing God would be greater than a non-existing God. Therefore we can only conceive of God as existing; so God exists.
This simple argument has mostly not found general favor. The definitive criticism was given by St. Thomas Aquinas (who otherwise thought that there were many ways to prove the existence of God): things cannot be "conceived" into existence. Defining a concept is one thing, proving that the thing exists is another. The principle involved is that, "Existence is not a predicate," i.e. existence is not like other attributes or qualities that are included in definitions. Existence is not part of the meaning of anything. Most modern philosophers have agreed with this, but every so often there is an oddball who is captivated by Anselm. Descartes was such an oddball.
Descartes' argument for God is not even as good as Anselm's. It runs something like this:
- I have in my mind an idea of perfection.
- Degrees of perfection correspond to degrees of reality.
- Every idea I have must have been caused by something that is at least as real [in objective reality, what Descartes calls "formal reality"] as what it is that the idea represents [in the subjective reality of my mind, what Descartes confusingly calls "objective reality"].
- Therefore, every idea I have must have been caused by something that is at least as perfect as what it is that the idea represents.
- Therefore, my idea of perfection must have been caused by the perfect thing.
- Therefore, the perfect thing exists.
- By definition, the perfect thing is God.
- Therefore, God exists.
Here Descartes uses "perfection" instead of Anselm's "greatness." The difficulties with the argument are, first, that the second premise is most questionable. Most Greek philosophers starting with Parmenides would have said that either something exists or it doesn't. "Degrees" of reality is a much later, in fact Neoplatonic, idea. The second problem is that the third premise is convoluted and fishy in the extreme. It means that Descartes is forced into arguing that our idea of infinity must have been caused by an infinite thing, since an infinite thing is more real than us or anything in us. But it seems obvious enough that our idea of infinity is simply the negation of finitude: the non-finite. The best that Descartes can ever do in justifying these two premises is argue that he can conceive them "clearly and distinctly" or "by the light of nature." "Clear and distinct ideas," are how Descartes claims something is self-evident, and something is self-evident if we know it to be true just by understanding it's meaning. That is very shaky ground in Descartes' system, for we must always be cautious about things that the Deceiving Demon could deceive us into believing. The only guarantee we have that our clear and distinct ideas are in fact true and reliable is that God would not deceive us about them. But then the existence of God is to be proven just in order that we can prove God reliable. Assuming the reliability of clear and distinct ideas so as to prove that God is reliable, so as to prove that clear and distinct ideas are reliable, makes for a logically circular argument: we assume what we wish to prove.
Descartes' argument for God violates both logic and his own method. In sweeping away the junk of history through methodical doubt, Descartes wasn't supposed to use anything from the past without justifying it. He is already violating that in the second mediation just by using concepts like "substance" and "essence," which are technical philosophical terms that Descartes has not made up himself. In the third meditation Descartes' use of the history of philosophy explodes out of control: technical terminology ("formal cause," etc.) flies thick and fast, the argument itself is inspired by Anselm, and the whole process is very far from the foundational program of starting from nothing. All by itself, it looks like a good proof of how philosophy cannot start over from nothing.
With the existence of God, presumably, proven, Descartes wraps things up in the sixth meditation: if God is the perfect thing, then he would not deceive us. That wouldn't be perfect. On the other hand, when it comes to our perceptions, God has set this all up and given us a very strong sense that all these things that we see are there. So, if God is no deceiver, these things really must be there. Therefore, external objects ("corporeal things") exist. Simple enough, but fatally flawed if the argument for the existence of God is itself defective.
In the fourth and fifth meditations Descartes does some tidying up. In the fourth he worries why there can be falsehood if God is reliable. The answer is that if we stuck to our clear and distinct ideas, there would be no falsehood; but our ambitions leap beyond those limits, so falsehood exists and is our own fault. Descartes does come to believe that all our clear and distinct ideas are innate: they are packed into the soul on its creation, like a box lunch. Most important is the idea of perfection, or the idea of God, itself, which is then rather like God's hallmark on the soul. Once we notice that idea, then life, the universe, and everything falls into place. Thus, Descartes eventually decides that the existence of God is better known to him than his own existence, even though he was certain about the latter first.
The fifth meditation says it is about the "essence" of material things. That is especially interesting since Descartes supposedly doesn't know yet whether material things existed. It's like, even if they don't exist, he knows what they are. That is Descartes the mathematician speaking. Through mathematics, especially geometry, he knows what matter is like -- extended, etc. He even knows that a vacuum is impossible: extended space is the same thing as material substance. This is the kind of thing that makes Descartes look very foolish as a scientist. But the important point, again, is not that Descartes is unscientific, but that he chose to rely too heavily on the role of mathematics in the nova scientia that Galileo had recently inaugurated. Others, like Francis Bacon (1561-1626), had relied too heavily on the role of observation in explaining the new knowledge; and Bacon wasn't a scientist, or a mathematician, at all. Descartes was. It really would not be until our own time that some understanding would begin to emerge of the interaction and interdependency between theory and observation, mathematics and experience in modern science. Even now the greatest mathematicians (e.g. Kurt Gödel, 1906-1978) tend to be kinds of Platonists at heart.
Copyright (c) 1996, 1998, 2006, 2007 Kelley L. Ross, Ph.D. All Rights Reserved
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