CH. 9 Descartes: Doubt and Certainty

Question 1

René Descartes’ – The Pursuit of Knowledge

Answer 1

RENE DESCARTES – (1596–1650)—the inventor of analytic geometry and founder of modern philosophy.

• Was the time of the Renaissance when established religious doctrines and traditional attitudes were being called into question.
  
  • This was the era of Galileo, Copernicus, Kepler, Bacon, Newton, and Martin Luther—thinkers who were dismantling the old ideological structures – the modern world was being born.
• He hoped that knowledge could be given a foundation as sturdy as that which buttressed mathematics.
• Descartes asked whether it was possible for anyone to possess knowledge.
  
  • Isn’t it obvious that we do in fact know things? Many philosophers thought the answer is not obvious at all. They ask:
    
    • If you have knowledge, how did you attain it? And if you possess it, how much do you possess—that is, what is the extent of your knowledge? Do you know only the contents of your own mind or only mathematical or logical truths? Do you know that there is a God, that ordinary physical objects exist, that there is an external world (one existing independently of your mind), that unobservable entities such as electrons are real, that other minds besides your own exist, that events have occurred before the present moment?
• Trying to find good answers to these is the main business of EPISTEMOLOGY – the philosophical study of knowledge – the branch of philosophy that systematically investigates whether, how, and to what extent we know things.
• Knowledge comes in different forms, and philosophy is usually concerned with only one of them – PROPOSITIONAL KNOWLEDGE. There are different types of knowledge:
  
  • Knowing what something feels like (for example, what influenza feels like)
  • Knowing how to do something (for example, how to throw a ball) constitutes another.
  • PROPOSITIONAL KNOWLEDGE – Knowing that something is the case (such as knowing that an elm tree grows in the quad) A proposition is a statement that is either true or false, an assertion that something is or is not a fact.
    
    • This kind of knowledge has been the main focus of philosophers.

The SCIENTIFIC REVOLUTION (dating roughly from the late sixteenth through the eighteenth centuries) upended the medieval worldview and ushered in a host of new ideas both in society and philosophy.

• Descartes was influenced by, and influenced, the scientific revolution, which in turn affected his contributions to philosophy.
• He was the genius who founded analytic geometry (remember Cartesian coordinates?), advanced the science of optics, wrote treatises on meteorology, and discovered how rainbows work.
  
  • In philosophy, he insisted that a radically different perspective was required.
• In light of the methods and findings of the “new sciences,” he saw that the old ideas had to go and that a new mechanistic and mathematical view of the world had to take its place.
  
  • In fact, he deemed mathematics a model for human understanding. He declared that the simple mathematical steps used to derive very complicated proofs “gave me occasion to suppose that all things which fall within the scope of human understanding are interconnected in the same way.”

Plato said that propositional knowledge os “justified true belief” and so it has three necessary and sufficient conditions:

1. ​You must believe it.
2. It must be true.
3. You must have good reasons for—be justified in believing it true.

SKEPTICISM – The view that we lack knowledge in some fundamental way. They hold that many or all of our beliefs are false or unfounded. And there is no way to be certain that anything we think we know is actually true.

• Some skeptics argue that we lack knowledge because we have no way of distinguishing between beliefs that we think constitute knowledge from beliefs that clearly do not constitute knowledge.
• For all we know, we could be hallucinating, dreaming, in the grips of an illusion, or mistaken for some other reason.
  
  • How do we know that we are not hallucinating or dreaming right now? Hallucinations and dreams can seem as real as our “normal” experience. If we cannot distinguish these two, the skeptic says, then we cannot have knowledge.
• Other skeptics raise doubts about the reliability of what we take to be our normal sources of knowledge—perception, memory, introspection, and reasoning.
  
  • We realize that all these sources are fallible, that they sometimes lead us into error. But skeptics ask how we know that these sources are not ALWAYS in error.
    
    • If all these sources are suspect, we cannot use one to check another.
      
      • EX: We cannot use our sense of sight to check the reliability of our sense of touch. And if we think one mode of perception is more trustworthy than the others, how do we know that? We seem forced once again into skepticism.
• Philosophers distinguish two ways to acquire knowledge:
  
  • ​Reason and Sense experience.
• A PRIORI – (Reason) It yields knowledge gained independently of or prior to sense experience.
  
  • EX: that all bachelors are unmarried, that all triangles have three sides, that 2 + 3 = 5, and that something is either a cat or not a cat. We need not do a survey of bachelors to see if they really are all unmarried; we can know this just by thinking about it. And we know that the statement “something is either a cat or not a cat” is true; it is a simple logical truth—and we know it without having to observe any cats.
    
    • RATIONALISTS – Believe that some or all of our knowledge about the world is gained independently of sense experience. That is, they maintain that some or all of our knowledge is a prior.
• A POSTERIORI – (Sensory) It gives us knowledge that depends entirely on sense experience.
  
  • EX: John the bachelor has red hair, that he just drew a triangle on paper, that he is holding five pencils, and that Tabby the cat is on the mat. To know these things, we must rely on our senses.​
    
    • EMPIRICISTS – Contend that our knowledge of the world comes solely from sense experience. We acquire knowledge entirely a posterior.
      
      • We may come to know logical and mathematical truths through reason, but we can know nothing about the world unless we use our senses.
• What can you know through reason alone?
  
  • Descartes would say that you can know a great deal. Without making any empirical observations.
    
    • EX: We know that nothing can both have a property and lack it at the same time, and that for any particular property, everything either has it or lacks it. Thus we know without looking that nothing can both be a dog and not be a dog at the same time, there are no square circles, and married bachelors don’t exist.
      
      • Some rationalists have gone further and asserted that reason alone can reveal the most important, basic truths about the world—such as “every event has a cause” and “the shortest distance between two points is a straight line.”
• Many of the greatest thinkers in history have taken the rationalist approach to knowledge, most notably Plato and Descartes.
  
  • Through reason, Descartes hopes to defeat skepticism.
    
    • His method is first to doubt everything that he cannot be certain of, a process that leaves him knowing hardly anything.
    • But through reason alone he soon uncovers what he considers to be self-evident;
    • from these certain truths, he derives other indubitable propositions.
    • In this way, he tries to build an edifice of knowledge that, like an inverted pyramid, rests on one or two rock-solid foundation stones that support all the others.
• Descartes, espousing the most influential rationalist theory, thinks sense experience is an unreliable source of knowledge, so he looks to reason to give all our knowledge a foundation as firm as that which supports unshakeable mathematical truths.
• The EMPIRICIST’s view of knowledge has been advanced most famously by the British empiricists, John Locke (1632–1704), George Berkeley (1685–1753), and DAVID HUME (1711–1776).
  
  • ​They want to turn Descartes’ pyramid right side up, resting all knowledge on a vast foundation of sense data (the content of our experience) that supports the upper stones.
• Hume probably has been most influential, arguing for an uncompromising Empiricism.
  
  • ​Hume holds that all our knowledge (aside from purely logical truths) is derived from sense perceptions or ideas about those perceptions.
  • Like other empiricists, he believes that the mind is empty —a blank slate—until experience gives it content.
    
    • Empiricists say that we can have knowledge of something only if it can be sensed, and any proposition that does not refer to what can be sensed is meaningless.
    • Guided by this latter empiricist principle, Hume is driven to skepticism about many things that others have taken for granted, including the existence of the external world, causation, a continuing self, religious doctrines, and inductive reasoning.
      
      • His skepticism arises because he thinks that even though all our knowledge is based on sense experience, we cannot know how the objects of our sense experience are related.
        
        • EX: We cannot know that there is a cause-and-effect relationship between associated objects. To infer such a connection is to go beyond what our senses tell us. Our notions of causal connections are merely matters of custom and habit.

Question 2

Plato’s Rationalism

Answer 2

PLATO’S RATIONALISM:

The great-grandfather of modern rationalism is Plato.

• ​Plato maintained that sense experience alone could not be the source of knowledge.
  
  • The PROBLEM with SENSORY INFORMATION – Many of his contemporaries assumed that since knowledge must be based on sense experience, and since sense experience can vary from person to person or culture to culture, relativism must be true. If one person says a grape is sour, and another says it’s sweet, there must be no objective fact of the matter, just truth relative to different persons.
    
    • Other thinkers thought that since our perceptions are often illusory, distorted, or otherwise mistaken, sense experience is not a reliable source of knowledge. And since our perceptions are the only possible route to knowledge, we must not know anything. Thus skepticism, they said, is the proper epistemological attitude.
• Plato thought that our perceptions were just as unreliable a guide to genuine knowledge as the relativists and skeptics assumed. But he argued that since we clearly do have knowledge, we must derive it from a reliable source—and that source has to be reason – (because it certainly isn’t the senses).
  
  • Plato deduced that we must be able to acquire knowledge because we can identify FALSE BELIEFS, and we obviously possess knowledge because we can grasp, through reason, mathematical, conceptual, and logical truths.
    
    • EX: We know that 2 + 5 = 7; that a triangle has three sides; and that if A is larger than B, and B is larger than C, then A is larger than C.
• ​Plato pointed out that these truths are objective: they are true regardless of what we think. We do not invent them out of our imaginations; we discover them.
  
  • Plato reasoned that if such truths are objective, they must also be about real things. They must refer to an independently existing, immaterial reality that is beyond sense experience.
  • In addition, he insisted, these truths must also be immutable and eternal, existing in the immaterial realm unchanged for all time. Only through our powers of reason can we reach beyond the physical world to take hold of real knowledge of fundamental truths (Forms).
    
    • Sense experience, in contrast, can yield only transitory, ever-changing information—mere opinion that is vastly inferior to everlasting truths.

INNATE IDEAS:

• Rationalists like Plato and Descartes typically accept the doctrine of INNATE IDEAS – the notion that we are born with some general ideas already in our minds.
  
  • Rationalists believe that the theory of innate ideas is the best explanation of why we can know some concepts a priori – that is, without ever experiencing them.
    
    • EX: We understand the idea of perfection even though we have never encountered a perfect object.
• How is it, Plato asks, that we seem to have knowledge of the Forms, however dimly, even though our senses can tell us nothing about them?
  
  • It’s as if these universals were already in our minds waiting to be uncovered. Plato’s answer—and the answer of most other rationalists—is the DOCTRINE OF INNATE KNOWLEDGE – at birth, our minds come equipped with conceptual content, ideas about the world that we can know a priori.
    
    • In Plato’s version of this view, knowledge of the Forms is present at the very beginning of our lives, inscribed in our minds (our immortal souls) in a previous existence. We are born with this knowledge. Accessing this knowledge then is a matter of using reason to recall what we previously knew in another life.
• Critics of innate ideas ask how we can possess knowledge that we are not aware of. Innate ideas are not learned; the mind is supposed to somehow always have them. But if we are unaware of them, how can they be or become knowledge?
  
  • Empiricists admit that our minds do possess innate cognitive capacities to learn certain concepts, but they maintain that having these capacities is a long way from having innate knowledge.

Question 3

Descartes’ Doubt

Answer 3

DESCARTES’ DOUBT:

• Descartes begins his quest for knowledge by first plunging into skepticism.
  
  • He sees that a great many things he thought he knew appear now to be false.
  • So he decides to “raze everything to the ground and begin again” from a firm foundation, doubting all beliefs except those that are “certain and indubitable,” beliefs that cannot possibly be false.
  • Only beliefs that are certain can count as knowledge.
    
    • If he has reason to doubt any of them, they are not knowledge.

René Descartes: Meditations on First Philosophy:

• I was convinced that I must once for all seriously undertake to rid myself of all the opinions which I had formerly accepted, and commence to build anew from the foundation, if I wanted to establish any firm and permanent structure in the sciences.
• But inasmuch as reason already persuades me that I ought no less carefully to withhold my assent from matters which are not entirely certain and indubitable than from those which appear to me manifestly to be false, if I am able to find in each one some reason to doubt, this will suffice to justify my rejecting the whole.

DREAM ARGUMENT – Descartes soon finds reason to doubt all beliefs based on sense experience, arriving at this conclusion via his famous DREAM ARGUMENT.

• “There are no certain indications by which we may clearly distinguish wakefulness from asleep.” Our dreams can seem like reality, and in dreams we often don’t know we are dreaming. So it is possible that we are dreaming now, he says, and that what we take to be the real world is in fact not real at all.
  
  • More to the point, it is possible that our sense experience—by which we presume to know material reality—is just a dream. If so, we can’t be certain about anything we think we know through our senses. Therefore, sense experience can yield no knowledge.

René Descartes: Meditations on First Philosophy (cont.):

• But it may be that although the senses sometimes deceive us concerning things which are hardly perceptible, or very far away, there are yet many others to be met with as to which we cannot reasonably have any doubt, although we recognise them by their means.
  
  • For example, there is the fact that I am here, seated by the fire, attired in a dressing gown, having this paper in my hands and other similar matters.…
• At the same time I must remember that I am a man, and that consequently I am in the habit of sleeping, and in my dreams representing to myself the same things or sometimes even less probable things, than do those who are insane in their waking moments. How often has it happened to me that in the night I dreamt that I found myself in this particular place, that I was dressed and seated near the fire, whilst in reality I was lying undressed in bed!
• At this moment it does indeed seem to me that it is with eyes awake that I am looking at this paper; that this head which I move is not asleep, that it is deliberately and of set purpose that I extend my hand and perceive it; what happens in sleep does not appear so clear nor so distinct as does all this. (It’s actually true that objects in dreams do NOT pass the reality test upon close inspection – try it and you will immediately realize you’re dreaming.)
• But in thinking over this I remind myself that on many occasions I have in sleep been deceived by similar illusions, and in dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep that I am lost in astonishment. And my astonishment is such that it is almost capable of persuading me that I now dream. (However, deliberate analysis of the dream world for the purpose of determining whether or not you are in a dream ALWAYS results in realizing that you are dreaming, if, in fact you are.)
• I can’t be sure that this is not the case. I can’t be certain that all my thoughts are not the work of an evil entity that infuses my mind with false sensations and ideas, making an external reality appear to exist.
• And if I am not certain of this, I can’t know anything that I previously thought I knew, including such seemingly obvious things as the truths of mathematics.

Living in the Matrix:

• Some philosophers think the skeptical implications of Matrix-type scenarios can be countered through an argument based in“inference to the best explanation”.

René Descartes: Meditations on First Philosophy (cont.):

• How do I know that I am not deceived every time that I add two and three, or count the sides of a square, or judge of things yet simpler can be imagined?

Descartes’ assumption is that knowledge requires certainty.

• He holds that for beliefs to count as knowledge, we must be certain of them—they must be so well supported as to be beyond all possible doubt.
• ​Criticism: But some philosophers claim that this requirement for knowledge sets the bar too high.
  • They reject Descartes’ skeptical arguments because they are convinced that knowledge demands not beyond-all-doubt certainty but only reasonable grounds for believing.
    
    • EX: After all, they say, we often claim to know many propositions that are not certain. We insist that we know that grass grows, that some dogs have fleas, that Africa exists, and that Abraham Lincoln lived and died in America—yet none of these statements are beyond all possible doubt.

Question 4

Descartes’ Certainty

Answer 4

DESCARTES’ CERTAINTY:

• Just when it seems that he can know nothing, he comes upon a truth that he cannot possibly doubt: he exists.

René Descartes: Meditations on First Philosophy:

• I shall proceed by setting aside all that in which the least doubt could be supposed to exist, just as if I had discovered that it was absolutely false; and I shall ever follow in this road until I have met with something which is certain, or at least, if I can do nothing else, until I have learned for certain that there is nothing in the world that is certain. Archimedes, in order that he might draw the terrestrial globe out of its place, and transport it elsewhere, demanded only that one point should be fixed and immoveable; in the same way I shall have the right to conceive high hopes if I am happy enough to discover one thing only which is certain and indubitable.
• I suppose, then, that all the things that I see are false; I persuade myself that nothing has ever existed of all that my fallacious memory represents to me. I consider that I possess no senses; I imagine that body, figure, extension, movement and place are but the fictions of my mind. What, then, can be esteemed as true? Perhaps nothing at all, unless that there is nothing in the world that is certain.…
• But how can I know there is not something different from those things that I have just considered, of which one cannot have the slightest doubt? Is there not some God, or some other being by whatever name we call it, who puts these reflections into my mind? That is not necessary, for is it not possible that I am capable of producing them myself? I myself, am I not at least something? But I have already denied that I had senses and body. Yet I hesitate, for what follows from that? Am I so dependent on body and senses that I cannot exist without these?
• But I was persuaded that there was nothing in all the world, that there was no heaven, no earth, that there were no minds, nor any bodies: was I not then likewise persuaded that I did not exist? Not at all; of a surety I myself did exist since I persuaded myself of something [or merely because I thought of something]. But there is some deceiver or other, very powerful and very cunning, who ever employs his ingenuity in deceiving me. Then without doubt I exist also if he deceives me, and let him deceive me as much as he will, he can never cause me to be nothing so long as I think that I am something. So that after having reflected well and carefully examined all things, we must come to the definite conclusion that this proposition: I am, I exist, is necessarily true each time that I pronounce it, or that I mentally conceive it.
• [I]t seems to me that already I can establish as a general rule that all things which I perceive very clearly and very distinctly are true.
  • (NOTE: WHY? We also proclaim dream things or hallucinations as being very clear to us at the time. And yet they are not true.)

In the very act of doubting, or of experiencing something contrived by the evil genius, Descartes finds unshakeable proof that he himself exists: “I think, therefore I am.”

• But can he know any more than this? He holds that he can indeed. He believes that he has discovered a first principle by which he can acquire knowledge despite his obvious fallibility:
  
  • He declares that if he perceives something clearly and distinctly, he must know it with certainty. Armed with this principle of knowledge acquisition.
    
    • (NOTE: But this declaration is based on the assumption that God is responsible for his thoughts and that God is NOT a deceiver, and so he will not be deceived in these “clear and distinct” perceptions.)
      
      • EX: He thinks he can know a great many things about the world. If he seems to perceive a flower, and his perception is clear and distinct, then the flower must exist and be very much as it appears to be.
• But why does Descartes think this principle is sound?
  
  • He argues that in his mind he has a clear and distinct notion of perfection, which must have a cause.
  • The cause of the idea of perfection, he says, must also be perfect,
  • and this perfect cause can only be a perfect God.
    
    • (NOTE: unfounded assumption)
  • A perfect God is no deceiver;
    
    • (NOTE: unfounded assumption)
  • such a God would not allow him to be deceived when he correctly applies his God-given ability to achieve knowledge—that is, when he follows the principle of clarity and distinctness.
    
    • (NOTE: unfounded assumption)
  • Therefore, when he perceives something clearly and distinctly, he knows it beyond all doubt. He has knowledge, and skepticism is defeated.
    
    • (NOTE: False Premises lead to false conclusions.)

René Descartes: Meditations on First Philosophy:

• That He is not a deceiver.
  
  • (NOTE – How do you know there is a god and that he is not a deceiver? This primary, unfounded assumption is the same criticism that undermined prior philosophers. – TJB)
• ​What I perceive clearly and distinctly cannot fail to be provided that I recollect having clearly and distinctly perceived it.
  
  • (NOTE: Says who? And how do you know that you are “clearly and distinctly” perceiving anything? – TJB
• I assure myself of the truth, I had been impelled to give my assent from reasons which I have since recognised to be less strong than I had at the time imagined them to be. What further objection can then be raised? That possibly I am dreaming (an objection I myself made a little while ago), or that all the thoughts which I now have are no more true than the phantasies of my dreams? But even though I slept the case would be the same, for all that is clearly present to my mind is absolutely true. (NOTE: False)

​How does Descartes try to show that the principle of clear and distinct ideas is justified? Does he, as his critics assert, argue in a circle?

(NOTE – ​​Things I perceive may be a dream.

1. There is a God.
2. All things depend on him.
3. He is not a deceiver.
4. Therefore he is not deceiving me.
5. Therefore what I clearly perceive must be true. –​ TJB)

• Descartes believes that he apprehends substantial truths about the world through reason. He would admit that through perception he learns simple facts such as the color of a flower and the position of the sun in the sky. But in many other cases, he says, knowledge of the external world is obtained through an “intuition of the mind,” not sense data.

René Descartes: Meditations on First Philosophy:

• Let us begin by considering the commonest matters, those which we believe to be the most distinctly comprehended, to wit, the bodies which we touch and see.
• Let us consider one body in particular.
  
  • For example, this piece of wax:
    
    • Finally all the things which are requisite to cause us distinctly to recognise a body, are met with in it. But notice that while I speak and approach the fire [the wax melts]
    • Does the same wax remain after this change? We must confess that it remains; none would judge otherwise.
  • We must then grant that … this piece of wax.…… is certainly the same,
    
    • But what must particularly be observed is that its perception is neither an act of vision, nor of touch, nor of imagination … but only an intuition of the mind.

RENE DESCARTES – (1596–1650) did his philosophical work in a time of intellectual, scientific, and religious change; an era of revolutionary new thinking that would eventually transform the Western world.

• Along the way, he reshaped mathematics by inventing coordinate geometry.
• He developed a rationalistic theory of knowledge whose starting point was a recognition of personal existence (“I think, therefore I am”).
• Reason is the source of substantial knowledge, and sense experience has only a subordinate role.
• He posited a stark division between mind and matter, with the two somehow interacting (an interaction that he could not adequately explain).

Does Descartes succeed in showing that knowledge of the external world is gained by an intuition of the mind?: (NOTE: No!)

• Descartes points out that although our senses tell us that the wax has changed through melting—that it has become a completely different object than it was before—our minds know better.
  
  • Through a rational intuition, our minds understand that the wax, though radically altered, remains a piece of wax. If we relied only on sense experience to inform us about the wax, we would have to conclude that the original object no longer exists.

Does his argument show that empiricism is false?:

• (NOTE – No! He seems to support empiricism as long as he “clearly” perceives something. – TJB)
• Many reject a key part of his argument, the premise asserting the existence of God. They doubt that Descartes—or anyone else—can infer the existence of God merely from the concept of God.
• HE begs the question, the fallacy of trying to establish the conclusion of an argument by using that conclusion as a premise.
  
  • Through his principle of clarity and distinctness, he tries to demonstrate that God exists. But then he attempts to establish the legitimacy of the principle by citing the existence of God.

Question 5

REVIEW NOTES

Answer 5

REVIEW NOTES:

The Pursuit Of Knowledge:

• Main question in epistemology is whether we have propositional knowledge and, if we do, how much we have.
• Propositional knowledge has three necessary and sufficient conditions:
  
  1. ​​You must believe it.
  2. It must be true.
  3. You must have good reasons for—be justified in—believing it true.