Discussion 6 PHILOSOPHY 101




Descartes, Locke, and the Persistence of Skepticism

Descartes, Locke, and the Persistence of Skepticism Continued

Descartes, Locke, and the Persistence of Skepticism Continued

Berkeley, Skepticism, and the Disappearance of Matter

Berkeley, Skepticism, and the Disappearance of Matter Continued

Berkeley, Skepticism, and the Disappearance of Matter Continued


Week Six

Locke’s Sensationalism and Berkeley’s Idealism

This week, we are examining some consequences from Descartes’ ‘rationalism’ and its problems, focusing on Locke’s ‘empiricism’ and Berkeley’s ‘idealism’. To what degree are ideas ‘innate’ within us, and to what extent are they produced only from our experiences of the world? If from experience, can we separate the world that produces the experience from the experience itself? If so, how? If not, does this mean that we are ‘trapped’ in a world of ideas?

And if we are trapped in a world of ideas, how do we guarantee that there is a world ‘out there’ independent of them? Even though he is so different from Descartes, Berkeley appeals to the same divine principle that Descartes does to guarantee the integrity of our ideas, even though doing so requires the ‘abolition of the material world’ as we currently understand it.

Weekly Objectives

Identify Locke’s Arguments Against Innate Ideas.
Describe how Descartes’ Ontological Dualism becomes Locke’s Epistemological Distinction between Primary and Secondary Qualities.
Evaluate the Split between Sensation and Reflection: Does it Undermine Locke’s Empiricism?
Describe Berkeley’s Challenge to Locke’s Distinction between Primary and Secondary Qualities.
Evaluate Berkeley’s Defense against Skepticism.
Explain Berkeley’s Esse est Percipi and the Omnipresent Mind of God.




Textbook: Modern Philosophy – John Locke – “An Essay Concerning Human Understanding”
Textbook: Modern Philosophy – George Berkeley – “Three Dialogues Between Hylas and Philonous”

Supplemental Resources

“John Locke” opens in a new tab

“George Berkeley” opens in a new tab

Required Activities

Discussion 6
Quiz 6
(Optional) Draft of Argument Analysis Paper


If you have questions regarding any of these activities, make sure to post those questions in the Open Forum.

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“The incorrigibility of the cogito is illustrated by
a story about Morris Raphael Cohen [a twentieth-century
philosopher of science and logician who taught at the City
University of New York]…A particularly intense and dedicated
student spent the night pondering Descartes’ Meditation II.
When he arrived in class unshaved, rumpled, and probably
wild-eyed, Cohen asked what was the matter. The student
replied that he had spent the night wondering whether he
existed. He then asked Cohen whether he did in fact exist.
Cohen is supposed to have replied…’Who wants to know’? ”
–R. G. Meyers, The Likelihood of Knowledge

Descartes, Locke, and the Persistence of Skepticism

Descartes’ solution to the problem of global skepticism at the beginning of Meditation II, the famous Cogito (I think), has had both its supporters and its detractors, though it seems quite clear that if there is awareness of doubt (a kind of thinking), there is awareness of that awareness as well, which constitutes self-awareness, and therefore self-knowledge. Of course, this really isn’t supposed to be an argument; rather it is a sort of intuitive knowledge: One is immediately aware of thinking about thinking, and it takes no argument to demonstrate such awareness. Descartes makes use of this fact as a premise in his arguments to defeat those of the skeptic (I must exist if I am to be deceived by my senses; I must exist no matter if I be dreaming or awake; I must exist if I am to be deceived by the malicious demon), but the intuition itself needs no argument to demonstrate it; intuition is supposed to be immediate, and, therefore, self-evidently true. Intuition also has a self-referential quality to it, which is why it seems so incorrigible, as the quote from Meyers above suggests. This intuitive, self-referential quality is also reminiscent of the flash of insight (grace?) experienced by Anselm in his insistence that if you genuinely know what ‘God’ means, you know that God exists! These sorts of self-referential (and therefore, self-contradictory if their truth be denied) issues arise in quite different contexts; for example:

“Now it is certainly easy to say to the single individual what Aristotle has already said: You have been begotten by your father and your mother; therefore in you the mating of two human beings—a species-act of human beings—has produced the human being…[But then you ask] Who begot the first man, and nature as a whole? I can only answer you: Your question is itself a product of abstraction…When you ask about the creation of nature and man, you are abstracting, in so doing, from man and nature. You postulate them as non-existent, and yet you want me to prove them to you as existing. Now I say to you: Give up your abstraction and you will also give up your question. Or if you want to hold on to your abstraction, then be consistent, and if you think of man and nature as non-existent, then think of yourself as non-existent, for you too are surely nature and man. Don’t think, don’t ask me, for as soon as you think and ask, your abstraction from the existence of nature and man has no meaning. Or are you such an egotist that you conceive everything as nothing, and yet want yourself to exist?” [Karl Marx, Economic and Philosophic Manuscripts of 1844]

As the editor of your textbook notes in his introduction to the work of George Berkeley (p. 620), “The answer to the famous conundrum ‘If a tree falls in the forest and no one hears it, does it make a sound’? is that if no one is perceiving it, it not only does not make a sound, the tree does not even exist! This would be quite literally true for Berkeley (whose name, by the way, is pronounced ‘Barclay’, not like the city in California), as we shall see. For Marx, as per the quote above, the situation would have been seen differently; the reason that there is no such tree isn’t because it isn’t being perceived, but because the stance of the question contains a contradiction; it would be like asking, “If there is no one around to hear the tree fall; nevertheless, if I were there to witness the event would it make a sound?” To which Marx might reply, “Your question is perverse; first you claim that no one is around to witness the event, and then you imagine yourself to be present to see if a noise is made!” It’s like asking a question about an unknown tree that you know about. Give up the abstraction or give up the question.; one can’t have both without being inconsistent. Or, to put it another way, this could only be an ‘imaginary’ tree which could, one supposes, make an ‘imaginary’ noise as it falls in the ‘imaginary’ forest!

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Descartes, Locke, and the Persistence of Skepticism Continued

As we saw last week, Descartes isn’t a skeptic; quite the contrary, he invokes the skeptical arguments in order to refute them once and for all. However, in this he apparently doesn’t succeed, not because of such issues as the ‘interaction problem’; but simply because once the emphasis is placed on the use of the senses as a source of knowledge, one is aware that one can never be absolutely sure the senses are giving us a true picture of the world. The doctrine that knowledge is always or mostly derived through sense-experience is empiricism, and its counterpart, that reason itself is the source of most or all of our reliable knowledge, is rationalism. These are epistemological doctrines concerning the nature and origin of knowledge. Descartes is usually considered to be a rationalist; Locke and Berkeley, the two philosophers we are reading this week, empiricists. These terms of epistemological demarcation are to be understood as having loose borders; there is no ‘purity’ to either of them, and even that arch-rationalist Plato required sense-experience as a basis upon which to recognize the distinction between the shadows on the cave wall and the truth, if only because sense-experience is too chaotic to be the sort of truth that Plato thought constituted genuine knowledge. And, as we shall see, Locke, who represents the empiricist tradition in epistemology about as well as anybody, also makes his compromises. Empiricists are acutely aware that the danger of global skepticism lurks in their commitment to sense-experience as the primary source of knowledge, and are constantly beating back that danger as best they can.

John Locke (1632-1704)

Empiricism itself gains strength as a result of the heretofore discussed scientific revolution (which, oddly enough, was also Platonic with its emphasis on the importance of mathematics for understanding the true nature of the world); however, its roots go much further back, at least to Aristotle, and it is preserved in the medieval tradition of the Scholastic philosophers (famously found, for example, in both St. Augustine and St. Thomas). “Nihil est in intellectu quod non prius in sensu.” Nothing is in the intellect that was not first in the senses. Descartes, of course, wouldn’t have agreed with this, seeing as how his idea of himself as a res cogitans (thinking substance) and his idea of God (infinite substance) do not depend at all on sense-experience, which, at the point in his Meditations where he discovers these ideas as ‘clear and distinct’ is still on the list of proscribed sources of such knowledge. For Descartes, these are, in some sense, innate ideas. And it is this notion that Locke first tries to refute in his work, An Essay Concerning Human Understanding. Try to pick out the arguments he is using from the readings from the text this week as a basis for beginning to answer the week’s discussion questions.

Of course, Locke was no stranger to the idea of ‘self-evident’ truths, and is often the philosophical figure referred to as most foundational to the American Republic: “We hold these truths to be self-evident,” writes Jefferson, that is, requiring no prior logical justification. For Locke, self-evident truths are intuitive knowledge, which is known with absolute certainty. The source of intuitive knowledge in Locke is the comparison by the mind of at least two different ideas, showing immediate agreement or disagreement simply through the comparison itself, without the need for any argument. He also believes that there is demonstrative knowledge, whereby the mind compares at least two ideas but requires reasoning (argument) in order to show agreement or disagreement (lacking the immediacy of intuitive knowledge). One way to bring out the difference is to use mathematical ideas; “that three are more than two,” Locke says, is intuitively known with immediacy, while most mathematical reasoning requires calculation (i.e., demonstration) in order to reach the required result. Demonstrative knowledge in Locke is as certain as intuitive knowledge, but, as he puts it, “not so easily known.”

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Descartes, Locke, and the Persistence of Skepticism Continued

On the other hand, sensitive knowledge, knowledge achieved through the senses directly, without what Locke calls reflection, lacks such certainty, even though it is the basis for all knowledge according to the ‘empiricist’ Locke. He wants to declare it certain and safe, because he is committed to his empiricism, and opposed to the doctrine of innate ideas, but the best he can do is this:

“But yet, if after all this any one will be so skeptical as to distrust his senses, and to affirm that all we see and hear, feel and taste, think and do, during our whole being, is but the series and deluding appearances of a long dream, whereof there is no reality; and therefore will question the existence of all things, or our knowledge of anything: I must desire him to consider that, if all be a dream, then he doth but dream that he makes the question, and so it is not much matter that a waking man should answer him. But yet, if he pleases, he may dream that I make him this answer, That the certainty of things existing in rerum natura (by the nature of things in nature itself) when we have the testimony of our senses for it is not only as great as our frame can attain to, but as our condition needs. For, our faculties being suited not to the full extent of being, nor to a perfect, clear, comprehensive knowledge of things free from all doubt and scruple; but to the preservation of us, in whom they are; and accommodated to the use of life: they serve to our purpose well enough, if they will but give us certain notice of those things, which are convenient or inconvenient to us. For he that sees a candle burning, and hath experimented the force of its flame by putting his finger in it will little doubt that this is something existing without him, which does him harm, and puts him to great pain: which is assurance enough, when no man requires greater certainty to govern his actions by than what is as certain as his actions themselves.”

There is that ‘self-referential’ quality again, regarding the dream argument: If one asks “Am I always dreaming,” one is, in order to maintain consistency, only dreaming that one is asking the question, which seems to undermine the importance of any answer to it that one might give, since one would only also be dreaming the answer! However, ultimately, what Locke is doing here is suggesting that though sense-experience gives us less certainty than intuition or demonstration, it is certainty enough to prevent us if we are diligent about our experience, to prevent us from experiencing the pain associated with being unnecessarily burned because of any denial of the reliability of such sensory information. Locke doesn’t so much refute the skeptic (like Descartes); instead, he simply denies the importance of Descartes’ methodological doubt: As long as Descartes wouldn’t allow the skeptical arguments to induce him to burn himself, their practical effect is nil and they do not undermine such certainty as is sufficient to get on with one’s life in an orderly fashion! And this is, according to Locke, all the certainty that we require.

Of course, it shouldn’t surprise us that skepticism remains an idea to be wrestled with, since we were first introduced to it during our first week, with Russell’s introduction of the distinctions between ‘sensation’, ‘sense-data’, and ‘physical object’. For the skeptic, the problem with the senses is that they stand on ‘one side’, while the world stands ‘on the other side’, and, like Humpty-Dumpty, once separated from one-another into (at least) two pieces, it is very hard, if not impossible, to put them back together again! We will see later on how important this issue becomes for Kant, who seeks to overcome the dichotomy between rationalism and empiricism, but in some sense makes skepticism a permanent part of the human condition.

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Berkeley, Skepticism, and the Disappearance of Matter

One of the interesting things about the relationship between Descartes and Locke is that, despite the distinction between rationalism and empiricism, there is so much that they agree on! For example, let’s take Locke’s distinction between primary and secondary qualities: Locke makes the distinction between those qualities present in our experience of objects that are really part of the objects themselves—‘solidity, extension, figure, and mobility’—and those which he calls ‘secondary qualities’—‘colors, sounds, tastes, etc.’ which aren’t ‘in’ the objects, but are the results of powers inherent in the objects whereby such qualities are induced as ideas in our minds. Ultimately for Descartes, of course, material body is res extensa, extended substance, all else being accidental properties induced in us depending upon circumstance, as Descartes’ example of the piece of wax showed in Meditation II. In fact, Locke refers to ‘wax or clay’ in his discussion of secondary qualities as well. They both agree that there is a distinction between the real properties that are inherent in the object, that define the object as an object, and those that are not really part of the object itself but are induced in us in and through our sensory relation to the object, whatever it may be.

But, now, the skeptic sees his opening: How do we know for sure that there is this property of extension (or, as Locke would have it, the various properties of solidity, extension, figure, and mobility), inherent in the object itself? In fact, how do we know that there is an object itself? Both Descartes and Locke agree that we cannot conceive of an object apart from having extension. However, how does this show, the skeptic wishes to know, that this isn’t merely another idea? That the idea of an object cannot be separated from the idea of extension seems only to demonstrate what Locke would regard as intuitive knowledge; that one knows immediately, without the need for a demonstration, that extension and object go together, but this really does seem to be what Locke calls an example of ‘ideas of relation’, a complex idea of comparison of one idea to another. And in fact, in a mirror image of what Descartes does in the Meditations, Locke insists that we know of our own existence through intuition, we know of God’s existence through demonstration, and the existence of all else through sensation. And what guarantees the accuracy of sensation in this regard, at least in a general way, and in a manner of certitude appropriate to it (which is less than our knowledge of our own existence and that of God’s existence)? For Descartes, it is that God is no deceiver; however, this just grants probability in the truth of many perceptions, never certainty, and doesn’t preclude human error in the interpretation of such experience. Sense-experience remains the least certain form of knowledge in Descartes, even though we can often count on it to be accurate; it is the least certain of the three modes of knowledge in Locke as well. So why, asks the skeptic, should we assume that any aspect of our experience of ‘the external world’, so to speak, demonstrates that there is an external reality ‘out there’, independent of our sensations and reflections upon it?

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Berkeley, Skepticism, and the Disappearance of Matter Continued

Absent Descartes’ rationalist argument that God is no deceiver, what guarantees do we have? One might ask, as Berkeley does, if empiricism inevitably leads to skepticism about the existence of the material realm altogether! And Berkeley answers the question with a resounding “Yes!” To defeat the skeptic, while remaining an empiricist, we must give up on the idea of res extensa, or rather give up the conceit that res extensa is itself anything else but another idea! For Berkeley, “esse est percipi,” “to be is to be perceived.” There is no ‘matter’; this doesn’t mean that the things we refer to as material don’t exist, mind you; it simply means that to call them material, as opposed to ‘mental’ is to mischaracterize what they really are; Descartes’ dualism is sacrificed in order to keep the skeptic at bay, and nothing at all exists outside of mind; all is res cogitans, pure and simple.

George Berkeley (1685-1753)

To go back to that imaginary tree in that imaginary forest: There is no such tree because a tree, like the forest it is part of, and everything else, must be perceived in order to be in the first place!

Well, as the editor of your textbook puts it, “Although Berkeley understood his philosophy to be common sense, his readers drew different conclusions. One prominent physician of his day claimed Berkeley was insane.” How ridiculous it would be to deny the existence of the material world (think of what the previously quoted Marx would say)! If ‘to be is to be perceived’ were true, wouldn’t that mean that things would go in and out of existence depending upon whether anyone were around to perceive them? If I’m the only one around, and I see an apple hanging from a tree, and I turn around in the other direction so that I no longer see either the apple or the tree, it ceases to exist? And then they come back into existence when I turn back to them and place them back in my sight? How absurd.

Well, of course, that’s not what Berkeley meant at all. And here, we get another visit from our old friend, Deus ex machina: What keeps both the apple and the tree in existence is that God perceives them, even when no one else is looking. God perceives all, at all times, and in all respects. The ‘external world’ may be external to human minds, but it is not external to mind itself, because it is not external to divine mind. Even if I am not looking at or attending to my apple tree, God willing, it will continue to bear fruit (and simply exist!) because God sees all.

One of the things that is most interesting about this is that if one’s initial reaction to it is something like “How unscientific!” one needs to be reminded of an interesting fact: That greatest representative of the scientific revolution we previously discussed, Isaac Newton, thought that all of space was ‘God’s sensorium’! That pre-eminent representative of the scientific mind would have agreed that God senses all, everywhere, all the time. Absent that, all would be chaos!

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Berkeley, Skepticism, and the Disappearance of Matter Continued

However, of course that was then, and this is now. So here is what one scientific perspective on the ‘now’ looks like:

“We’ve certainly come a long way since the ancient Greek atomists speculated about the nature of material substance 2,500 years ago. But for much of this time we’ve held to the conviction that matter is a fundamental part of our physical universe. We’ve been convinced that it is matter that has energy. And, although matter may be reducible to microscopic constituents, for a long time we believed that these would still be recognizable as matter—they would still possess the primary quality of mass.

Modern physics teaches us something rather different, and deeply counter-intuitive. As we worked our way ever inward—matter into atoms, atoms into sub-atomic particles, sub-atomic particles into quantum fields and forces—we lost sight of matter completely. Matter lost its tangibility. It lost its primacy as mass became a secondary quality, the result of interactions between intangible quantum fields. What we recognize as mass is a behavior of these quantum fields; it is not a property that belongs or is necessarily intrinsic to them.

Despite the fact that our physical world is filled with hard and heavy things, it is instead the energy of quantum fields that reigns supreme. Mass becomes simply a physical manifestation of that energy, rather than the other way around.

This is conceptually quite shocking, but at the same time extraordinarily appealing. The great unifying feature of the universe is the energy of quantum fields, not hard, impenetrable atoms. Perhaps this is not quite the dream that philosophers might have held fast to, but a dream nevertheless.” [Jim Baggott, “Physics has Demoted Mass: Modern Physics has taught us that mass is not an intrinsic property.” opens in a new tab

Berkeley’s Three Dialogues Between Hylas and Philonous, in Opposition to Skeptics and Atheists represents Berkeley’s attempt to defeat skepticism by embracing the doctrine of idealism. Though there are many versions of idealism throughout the history of philosophy; in general, idealism is the view that all reality is what Descartes would have called ‘res cogitans’; ‘thinking substance’ or ‘mental stuff’. It is usually counterposed to the doctrine of materialism, the idea that all reality is physical in nature. There are many versions of this doctrine as well, and, like the distinction between empiricism and rationalism, the boundaries between idealism and materialism aren’t well-defined, either. In this work, which returns to the dialogue form we found in Plato, Philonous (‘mind-lover’) represents Berkeley, while Hylas represents the ‘materialist’ (Hylē being an ancient Greek term for matter). There are many arguments made in the three conversations in support of Berkeley’s position; you will be asked in this week’s discussion session to pick out a couple and formulate them and comment upon them.

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