Late Modern Philosophy Test 1

Can We Have an Idea of God? One interesting objection that Hylas raises to the scheme that Philonus (i.e. Berkeley) has provided is the claim that we can have no idea of God. Since an idea can only resemble an idea, and God or other minds are active, non-idea type things, we can have no idea of God, nor of the self. And this seems to imply that there can be no meaningful talk about God or other minds. This would be a serious difficulty for the Berkeleyan philosophy. What's the reply?

"I admit I have properly no idea, either of God or any other spirit; for these, being active, cannot be represented by things perfectly inert as our ideas are. I do nevertheless know that I, who am a spirit or thinking substance, exist as certainly as I know my ideas exist," (A&W, p. 527). This leads to the doctrine that we can have a notion of spirit, or of God, which are active beings whose existence we infer even though we have no immediate perception of them. However, Hylas asks why can't he have a notion of matter? Berkeley states you can only have a notion of something that is coherent and consistent and matter is neither. However, a huge problem occurs. How can we determine what is coherent? You can't say we have a coherent notion of mysterious things such as the Trinity. The best that Berkeley can do on this score is punt and fall back on the claim that matter is incoherent -- but that incoherence seems to concern a dualistic treatment of matter and leaves a pure materialism more or less untouched.

How does Berkeley argue for the existence of God?

1. Inference leads us to God - He looks at our perception and gives three hypotheses. First, matter which we have found to not exists, second, ideas are self-caused which is false because ideas and perceptions need other causes, so it must be number three which is some other mind. This is our best explanation. All sensible things must be perceived by God. If we give up matter, it not only destroys skepticism but atheism which is a double win!

What is Berkeley's truth? What problems does he face? How does he respond?

1. To exist = to be perceived 2. Real Things = what we perceive (Case for Authority Senses) However, 2 Problems. 1. This idea is so radical 2. The Biggest - Physics requires matter. He states the perceivable traits are things we know how to measure. We don't need matter but wants the right kind of numbers. Wants to keep Newtonian Physics but with a twist. He wants Descriptive Laws instead of causal laws. All Physics discoveries are just discoveries of patterns. Doesn't deny causes just doesn't care about them.

How does Hylas define sensible things? Why does he change his definition and what does he change it to?

A key move in the Three Dialogues is the definition of the term 'sensible things' as "Those things that are perceived by the senses" (A&W 497). A sensible thing, thus understood, must be perceived immediately and without inference. The point here is that I might say that I saw the Pope on television yesterday, but what I really saw was an image on a screen, which image was transmitted by a signal that had its origins in Rome. (Of course, If I said "I saw the Pope on my TV last night," I might have meant that I saw him sitting on top my TV set; but we'll leave that disturbing possibility aside). Likewise, I might be inclined to say that I saw a homeless man sleeping on a park bench this morning, when in fact I inferred that the guy was homeless because he was shabbily dressed and was sleeping on the bench. But, for all I know, he might have been a tenured professor of computer science at USF who was just relaxing in the morning sun. Thus, Hyals agrees to the definition that by sensible things I mean those only which are perceived by sense and that in truth the senses perceive nothing which they do not perceive immediately, for they make no inferences. The deducing therefore of causes or occasions from effects and appearances, which alone are perceived by sense, entirely relates to reason. (A&W, 497) This raises a further question: can sensible things exist without a mind to perceive them?

What reasoning does Hylas give after abstract ideas fail?

Another way that Hylas tries to avoid the conclusion that all sensible objects are "in the mind" is to draw a distinction between the act of perception and the object perceived. The point here is that we may grant that the act of sensation can only be "in the mind," but the object sensed is something entirely distinct. The problem here is that we don't seem to be terribly active in perception. When the lights are on and your eyes are open, you have no choice over what you perceive; thus, there seems to be no act of perception, but only the mind's reception of ideas from some source.

How did the Aristotelians and Descartes view the natural world?

Aristotelians held that the natural world was to be seen in terms of concepts such as form and matter, Descartes argued that the natural world should be understood purely mechanically - i.e. as a gigantic machine that produced its effects by the motion and impact of material bodies.

How is Philonous not a skeptic? How does Hylas respond?

At first, a skeptic is defined a one who "doubts of everything". But, by this standard, someone who denies the existence of matter is not a skeptic, since his denial of material substance does not express doubt but a positive conviction that there is no such thing. The result is that Hylas reformulates his definition of the skeptic to include one who "denies the reality and truth of things". With this as an operative definition of skepticism, the task is then to determine whether Hylas or Philonous denies the reality and truth of things. Berkeley's strategy will be to show that it is Hylas who continually questions the reality of those things that common sense takes for granted.

How does Berkeley argue for the existence of God? What does La Mettrie think of such a project?

Berkeley argues from the existence of sensible things ("ideas of sense") to the existence of God by a kind of inference to the best explanation. He claims that our perceptual states must have some kind of explanation or other, and notes that everyone grants that minds have the causal power to generate ideas. This is shown, for instance, by the fact that the mind can frame ideas of imagination or recollection. But we don't control our perceptual states in the case of immediate perception: when the lights are on and your ideas are open, you have no control over what you see. Thus, the mind is not the cause of its perceptions. What else could be? Well, sensory ideas cannot cause themselves, so we can rule that out. Further, Berkeley takes it to have been firmly established that matter cannot exist, so that cannot figure in the explanation. So, it must be some other mind that causes our sensations. This mind is clearly very powerful, benevolent, and wise. Obviously, it has to be God who is the immediate cause of our sensations. Happy days! La Mettrie, obviously, will have none of this. In particular, he is emphatic in claiming that we can account for perceptual states in purely material terms, so a main premise of Berkeley's argument is rejected. Further, he had little good to say about the whole project of theology, so it is unlikely that he would have been much enamored of the conclusion.

What does Materialism lead to according to Berkeley? How does La Mettrie fit into these claims.

Berkeley believes Materialism leads to Atheism and Skepticism. La Mettrie says that he does not "call in question the existence of a supreme being" and declares that "the greatest degree of probability is for it" (p. 54). At the same time, he dismisses the notion of God as essentially irrelevant to human concerns, being "a theoretical truth that is of no use in practice." Even if he was not an atheist, however, La Mettrie was clearly a freethinking opponent of traditional religion. La Mettrie, however, rejected dualism and simply identifies thought with motions in the brain. Given this account of cognition, the traditional skeptical arguments can't really get rolling. Indeed, La Mettrie's epistemology simply ignores (or even dismisses) skeptical doubts. He recommends that we gather empirical data in the style of the "medical philosophers" and set aside merely theoretical worries about the human capacity for knowledge. Thus, Berkeley's insistence that materialism implies skepticism seems rather wide of the mark.

How does Philonous show matter is inconsistent and its existence is impossible at the end of Dialogue 2?

Berkeley closes the second dialogue with an argument to the effect that the very existence of matter is an impossibility. The grounds of this incoherence are that the concept of matter is a self-contradiction: it is both sensible and yet insensible, it is inert yet causally active. Conclusion: "in that which you call the obscure, indefinite sense of the word matter, it is plain, by your own confession, there was included no idea at all, no sense except an unknown sense, which is the same thing as none," (A&W 524).

How does Berkeley defeat skepticism?

Berkeley has already defined "real things" as what we directly and immediately perceive. So, we can defeat skepticism by drawing a stable distinction between what's real (objects of sense perception) and what's illusory (things we imagine or misperceive).

What does Berkeley make of the claim that we can frame an idea of matter as an unknown substratum in which sensible qualities inhere?

Berkeley holds that there is no sense to this claim, because there is no way to comprehend how ideas (sensible things) can somehow be supported by or inhere in a vague "something" that is radically distinct from sensible things.

How did Berkeley view free thinkers?

Berkeley loathed freethinkers and regarded the refutation of freethinking as an absolutely essential task for philosophy. It is worth pointing out that a large part of what motivates this trend is the notion that "natural philosophy" in the style of Newton is sufficient to explain all the phenomena of the natural world. For Berkeley, then, the challenge is to retain the successes of Newtonian physics while separating it from the natural theology with which it had become associated.

What, according to Berkeley, are "real things" as opposed to illusions?

Berkeley says that real things are "those things we perceive by sense."In a case of illusion, what one sees is really there, but the error arises from inference about what other experiences one might have. The partially submerged stick really does appear bent as you see it, but you're wrong if you think it will still look bent when removed from the water.

Berkeley denies the existence of matter. How does he explain the success of physical theories like Newton's theory of gravitation, if there are no material objects?

Berkeley takes the success of Newtonian physics seriously, but he offers a way of understanding physical theories that does not presuppose the existence of material substances. In Berkeley's scheme of things, the goal of a physical theory is to provide a purely descriptive account of the way the world works, without delving into the consideration of ultimate causes. Physics, thus understood, is consistent with Berkeley's metaphysics because it doesn't actually need to talk about unobserved material bodies. The fundamental laws of mechanics can be read in accord with phenomenalism to talk about observed processes and objects. In the Principles, Three Dialogues, and On Motion, Berkeley stresses that we need not make reference to material bodies (or mysterious things like attractive forces) to make physics come out right. Thus, when taken to be about the observable behavior of observable entities, Newtonian physics is consistent with Berkeley's phenomenalism.

Can The Unextended Mind Contain Extended Things?

Berkeley's (rather weak) response here is that when we speak of extended collections of ideas being "in the mind" such talk "should not be understood in the gross or literal sense." To say that something is "in the mind" means simply that it is perceived, not that it is contained in the way that a pint of beer is contained in a glass. The ultimate consequence here is that Berkeley takes the concept of perception to be incapable of analysis, and as a basic notion for which no further account need be given.

Berkeley argues against the "modern way" of explaining sensation in terms of motions communicated from the sense organs to the brain, which then frames various ideas in the mind. Why does he think this is a useless account of sensation? Why does La Mettrie think it is clearly correct?

Berkeley's main argument is that there is no comprehensible sense in which an inert, non-mental thing like matter could ever "give rise" to purely mental phenomena like ideas. The main assumption here is that, by its nature, the mind is non-material, and there can be no coherent way to bridge the "explanatory gap" that separates the world of physical things and the non- physical realm of the mind. Given this assumption of a fairly strong kind of dualism, Berkeley has little trouble demolishing the "modern way" of accounting for perception. And, of course, in the Three Dialogues, Hylas quickly gives up on the whole project anyway. La Mettrie rejects the fundamental notion that the mind can only be understood in purely "spiritualist" or non-material terms. Thus, he is quite happy to conclude that thought is a process carried out by the brain in much the same way that circulation is a process carried out by the heart and blood vessels.

How are Berkeley and Malbraunch similar? How does Berkeley feel about this comparison?

Berkeley's proof of the existence of God has the consequence that God is the immediate cause of all our "ideas of sense." That is to say, when you look out the window and see clouds in the sky, this visual content is not produced in your mind by reflected rays of light stimulating various tissues in your optical sensory system, but rather by God immediately putting the relevant ideas into your mind. This has some similarity with a doctrine of the French philosopher Nicholas Malebranche (1638-1715) who was a proponent of the whacky metaphysical view known as "occasionalism" and who also proposed that "we see all things in God." Berkeley states I shall not therefore be surprised if some men imagine that I run into the enthusiasm of Malebranche, though in truth I am very remote from it. He builds on the most abstract general ideas, which I entirely disclaim. He asserts an absolute external world, which I deny. He maintains that we are deceived by our senses and do not know the real natures or the true forms and figures of extended beings - to all of which I hold the direct contrary. So that, upon the whole, there are no principles more fundamentally opposite than his and mine. (A & W, 478)

The Distinction Between Primary and Secondary Qualities

Descartes held that all that is essential to material bodies is the fact that they are extended (i.e., they take up space). All the other qualities we normally attribute to bodies (color, temperature, taste, odor, etc.) merely arise from the interaction of our sensory apparatus with extended material things. So, the qualities that an object has simply in virtue of being extended (shape, motion, etc.) are "truly real" or primary; the rest are in some sense subjective and not fully real.

What was the point of Descartes using the method of doubt?

Descartes thought that a secure body of knowledge could be established and rendered immune from the challenges of skepticism. A central part of this project was the claim that the senses are not a reliable way of obtaining knowledge. Phenomena such as illusions and dreams show that the senses can deceive us, so Descartes held that certainty must reside in pure concepts of the intellect, not the data of the senses.

How does Berkeley view matter? What is skepticism? Why, according to Philonous, does the belief in material substance lead to skepticism?

He denies the existence of matter and claims it leads to skepticism. In general, skepticism is the denial of claims to knowledge. The skeptic claims that, so far as he or she can tell, there are no conclusive grounds to believe in a particular knowledge claim. One common form of skepticism is the claim that we cannot know what the world is really like or how it operates. According to Berkeley (in the guise of Philonous), belief in material substance promotes this kind of skepticism because he assumes that the mind must be immaterial and aware only of various ideas; but a realm of material objects "on the other side" of our ideas must inevitably be conjectural and unknowable. The basic skeptical problem here is to account for how our (immaterial) ideas might "match up" with and resemble a realm of material substances. Likewise, it becomes difficult to explain how material processes taking place in the nervous system can produce ideas in a mind. This argument is effective only if a dualistic conception of mind and matter is presupposed - a pure materialist who identifies thought with the action of a material body faces no such "gap" between ideas and material things.

How does Berkeley show Primary Qualities are also observer dependent?

He gives 2 Arguments. 1. Parity Argument - Illusions, Ex. Mice food to a human looks small, but to a mouse it looks normal. 2. Inseparable Argument - If you can't separate your idea from sensible ideas, they can't be mind dependent, if you can't the secondary qualities without the mind, you can't have primary

What was Hylas's biggest mistake?

He grants ideas are sensible objects

How does La Mettrie approach Descartes's view of the mind?

He has two big problems. 1. The Problem of Interaction - The most obvious difficulty for the Cartesian standpoint is the difficulty of explaining how mind and matter can interact. La Mettrie makes fun of the notion of "immateriality" which he describes as "a big word empty of meaning," and insists that the appeal to some sort of immaterial thinking principle is completely useless. 2. The Attribution of Thought to Non-humans. A further problem with the Cartesian approach is that it requires a radical division between humans and non-human animals. If Descartes is correct, we can fully understand animals as complex machines which, however, lack the capacity for thought. Descartes gave complex and detailed empirical arguments designed to show that phenomena like circulation, respiration, and locomotion in animals have completely mechanical explanations. From this, he inferred that animals must be more than machines. However, it is pretty obvious that animals do have mental lives, so this much of Cartesianism looks like a complete mess.

How does Berkeley respond to the question, "Can two people see the same thing?"

His approach is to downplay the significance of the notion of "sameness." In ordinary talk and though we are happy enough to say that people see the same thing, meaning thereby that they agree in their descriptions of their perceptions. But "whether philosophers shall think fit to call a thing the same or not, is, I conceive, of small importance."

Berkeley's biggest problem with eliminating matter is what?

His biggest problem is illusions. Hylas raises another familiar argument against Berkeley's idealism when he charges that denying the existence of matter makes everything illusory, or at least fails to distinguish reality from illusion: "according to your notions, what difference is there between real things and chimeras formed by the imagination or the visions of a dream, since they are all equally in the mind?" (A&W 489) The reply is straightforward -- real things are those sensible objects we apprehend by immediate perception, whereas imaginary beings are less vivid and are wholly dependent upon our will. This connects to the thesis that the laws of nature are simply those "rules" by which God, the great Author of Nature, produces sensible objects (i.e. ideas) in our minds. For Berkeley, illusions arise from a false inference/judgement about what "would be" perceived.

What does Hylas propose after he likes Philonous's explanation for God? How does Philonous respond? What is Hylas's next suggestion? What is his last attempt?

Hylas wants to say matter is a subordinate cause. There should be a third thing outside of mind and idea. Philonous says Hylas is just going back to Dualism and that it will get them no where. Hylas then suggest God uses matter as his instrument. Philonous again denies this and states why would God even need an instrument. Last, Hylas states matter may be an "occasion" for God to produce sensations in us. This also fails to get anywhere -- the regular sequence of ideas that is the course of nature is explained sufficiently by reference to the power and wisdom of God, whose volitions Berkeley characterizes as the "Laws of Nature."

How does Hylas change his definition of qualities? How does Philonous respond?

In attempting to avoid this result, Hylas invokes a distinction between perceived extension and "absolute" or "abstract" extension. According to Hylas, we may grant that relative or perceivable space exists only in the mind of a perceiver, but there is an abstract notion of space that is mind independent. Philonous has no time for this garbage. Instead he states, so, we reason "abstractly" by having a fully determinate idea before the mind, but disregarding some aspects of it when we formulate a general law. For instance, in framing the physical principle "Every action has an equal and opposite reaction" I might imagine a billiard ball rolling toward the cushion of a pool table, striking it, and rebounding with an equal and opposite velocity.

How does La Mettrie explain imaginations?

Instead, La Mettrie claims that "imagination" is the fundamental faculty of mind: "only the imagination perceives; the imagination represents all objects with the words and figures that characterize them; and, thus again, the imagination is the soul since it plays all the roles" (p. 44). The term imagination is a bit confusing here, since La Mettrie basically takes it to be the faculty of forming images; so imagination doesn't just mean the power to frame fictional objects, but the capacity to perceive external things. A better term might be 'sensation'. A further consequence is that there is no soul, if by the term 'soul' one understands some kind of immaterial self that survives death.

What evidence does La Mettrie give for thinking that the mind is a complex machine?

La Mettrie's argument is that a comparison of the neuroanatomy of humans and other animals shows a significant similarity. Since nobody (except for crazed Cartesians) doubts that animals have minds, but nobody thinks such animal minds are immaterial, we should conclude the same of humans.

Where is the moral obligation for La Mettrie?

La Mettrie's response is to claim that human action is right or wrong insofar as it conforms to what he calls the "natural law." This law is not some kind of divine command delivered on stone tablets, but a simple principle of enlightened self-interest. The law can be summed up as "a feeling that teaches us what we must not do on the basis of what we would not have someone else to do to us" (p. 53). The point is that we are obligated to avoid harming others, and the ultimate basis for this is that we seek our own good and desire not to be harmed by others. This sort of reasoning seems not to require a non-material soul that does our moral thinking for us: instead, morality is simply a system of rules that work to our general advantage, and calculation of advantage requires nothing more than enlightened self-interest. It should be clear that this way of thinking about morality dispenses without God, and that raises the question of whether La Mettrie advocates atheism.

What does La Mettrie say about the Explanatory Gap ?

LaMettrie's response to this problem is to ignore it: he simply identifies the psychological with the physical and leaves it at that. As we'll see, this is not a problem that is so easily dismissed.

Why, according to La Mettrie, are the best philosophers those who are also physicians?

On La Mettrie's analysis, philosophers who have studied medicine (like La Mettrie himself, for example) are accustomed to judge matters on the basis of empirical evidence and argument rather than fanciful abstract theories that are divorced from experience.

What is Berkeley's view on common sense? How does Hylas respond? How does Berkeley respond?

One of Berkeley's favorite claims was that he was the defender of common sense, a philosopher whose opinions did not deviate from the ordinary view of philosophically untutored "plain folks." An obvious objection is that ordinary people just don't believe that the world consists only of minds and ideas. As Hylas frames the point: "Ask the first man you meet, and he shall tell you, to be perceived is one thing and to exist is another." (A&W, 488). Berkeley's reply is that, on the contrary; the average person would say he believes that a tree exists because he can see it.

What does Berkeley say needs to be shown in order for him to believe in matter?

One useful way of motivating Berkeley's seemingly bizarre denial of material substance is to focus on the concept of explanation and ask what role matter might play in the explanation of phenomena. As traditionally conceived in Berkeley's day, matter was an entirely inert, passive "stuff" that cannot initiate its own motion or effect much of anything. Indeed, Descartes held that the essence of material bodies is simply extension: all they really do is take up space. Likewise, Locke held it the cohesion of bodies and the communication of motion by impulse to be a matter of great puzzlement. Even worse, dualists like Descartes and Locke confessed that they had absolutely no clue how a material process (like the motion of nerves and the stimulation of various parts of the sensory apparatus) can result in the production of mental events like perception. Berkeley seizes on these sorts of worries and offers the challenge that "if you can prove that any philosopher has explained the production of any one idea in our minds by the help of matter, I shall forever acquiesce an look on all that has been said against it as nothing" (A&W, p. 533). As we will see, La Mettrie is happy to take up this challenge.

What is Phenomenalism?

Phenomenalism is a thesis about the meaning of empirical statements and holds that any meaningful empirical claim must be translatable into claims about actual or potential experiences

For Philonous, what is the only cause?

Philonous also stresses the point (which will be important later) that the only cause can be a volition or act of will.

Why did Philonous say Direct Realism doesn't work?

Somethings taste different to different people, or colors to colorblind people look different

Descartes Proof of God's Existence

The Cartesian program would go essentially nowhere unless there was a benevolent God on the scene to guarantee that our "clear and distinct" concepts must be true. Thus, a common theme in seventeenth and eighteenth century thought is the search for a reliable and convincing means of proving the existence of God.

What is Descartes method of doubt?

The basic idea here is that one should subject one's beliefs to a rigorous process of doubt in order to uncover unassailable foundational principles that can survive any skeptical challenge.

What is Berkeley's master argument?

The final nail in the coffin of material substance is Berkeley's argument that the very concept is incoherent. Matter, by definition, is supposed to be something unperceivable (since we only immediately perceive our own ideas). Thus, if matter exists, it must be an unperceivable thing. But can we even think of something unperceived? Berkeley's so-called "master argument" is an attempt to show that we cannot. The argument (summarized on p 511 of A&W) reasons as follows: suppose you try to think of an unperceived object, such as a tree in the forest with nobody around to perceive it. In so doing, you frame an idea of a tree; this imagined tree is perceived by you, therefore you cannot frame the concept of a thing that is literally unperceivable.

What is the point of the Three Dialogues?

The first dialogue is devoted more or less exclusively to arguments against the existence of matter; the second draws positive consequences from the denial of matter (most notably the existence of God); the third and final dialogue sets out objections to Berkeley's immaterialism, which his spokesman Philonous answers. Throughout it all, Berkeley insists that his principles are those that are embraced by "the man of common sense" who has not been tainted by the "new philosophy" of Descartes, Locke, etc.

What are two important sources for La Mettrie?

The first of these is research into neurophysiology (notably Albrecht Haller's work on the relationship between muscles and nerves), the second is microscopy, which shows that vast segments of the supposedly inanimate material world are actually teeming with life. LaMettrie saw himself as a one who extended these scientific advances into the realm of philosophy.

How is La Mettrie a free thinker?

The point, then, is that we should use empirical evidence and reasoning to find out how the world works. I particular, we can draw inferences from the features of animals ("animated bodies") to understand such processes as circulation, digestion, respiration, locomotion, and thought. Having done this, we see that there is no reason to think that supernatural revelation has anything to contribute to our understanding of the world.

What is La Mettrie's Main Argument?

The results of comparative anatomy show that the neural structure of mammals is strikingly similar across species, and there are also strong similarities in other aspects of animal anatomy. Given this data, it is unreasonable to think that there is some kind of "metaphysical gap" separating human beings from the rest of nature. As he puts it, "The transition from animals to man is not abrupt" (p. 41). Furthermore, we know that humans are capable of thought (even Descartes figured this one out). So, there is no principled reason for thinking that other animals must lack minds. But we are perfectly happy in thinking of animals as complex machines, so there is no reason (aside from prejudice or obscure religious conviction) to think that humans are not also complex machines.

What is the modern way? How is the modern way wrong?

The soul resides in the brain and extends out ideas to the body. This, obviously, raises the familiar mind/body problem that afflicts any sort of substance dualism. If the brain is a "sensible thing" then it is an immediately perceivable collection of ideas, which gets Hylas nowhere. If it is not a sensible thing, then he needs to explain how insensible motions in a non-sensible thing can produce any mental contents at all. From this, Hylas is forced to admit that he is a complete and utter skeptic. His comfort is that, by denying matter, Philonous "is as much a skeptic as I am."

How does Berkeley respond to Hylas's claim that he is going against Scripture?

The way out of this little problem is simple enough: when it is written that things were created in a given order, "I imagine that if I had been present at the creation, I should have seen things produced into being, that is, become perceptible, in the order described." This is the same way that Berkeley handles questions about the continued existence of things unperceived by any finite mind. When you close the door to your refrigerator, its contents are not demolished, only to be suddenly re-created when next you open the door. Rather, the continued existence of the fridge contents amounts to God's keeping them around as objects of the Divine Understanding.

How does Philonous show secondary and primary qualities only exist in the mind?

They are both observers dependent. Secondary qualities such as color, can be perceived differently by different people based on their condition. This argument is called the Parity Argument and it is used for primary qualities as well. The same thing can be said about shape, size, number, or motion. Example of water being warm to one hand but cold to another. Philonous also gives the "Separability Argument" or the Inseparability argument. This states that since we cannot frame an idea of a primary quality separate from all sensible secondary qualities, the primary qualities must also exist only "in the mind."

What does Berkeley mean by "Matter is explanatory irrelevance?"

This is actually more of an attack on Dualism. If you load up on Dualism, you get too many useless material bodies and how can they have an impact on ideas and sensations.

Difference between revealed religion and natural religion

Unlike proponents of "revealed religion" who insisted that certain tenets could not be rationally criticized, the project of natural religion was to show that a careful and impartial examination of the natural world would lead one to see that there must be a God.

How does belief in material things lead to skepticism?

You are, therefore, by your principles forced to deny the reality of sensible things, since you made it to consist in an absolute existence exterior to the mind. That is to say, you are a downright skeptic. So I have gained my point, which was to show your principles lead to skepticism. (A&W, p. 514) Thus, belief in material objects gives rise to skeptical conclusions.

Who are the two characters in the Three Dialogues and what do their names mean?

the characters in the Three Dialogues are named Hylas and Philonous. These are derived from the Greek word for 'matter' (hyle) and 'friend of the mind' (philonous).