The Three Dialogues of Hylas and Philonous

A Brief Look at Dialogues One and Two

Berkeley's main arguments in the three dialogues can be reduced to these themes:

Dialogue 1: Matter is inconceivable.
Dialogue 2: Matter plays no functional role in explanation.
Dialogue 3: Idealism is consistent with everyday experience.

Dialogue 1: The Inconceivability of Matter

Although Berkeley's aims in dialogue 1 are numerous, I'd like to simplify his attacks to two. First, he wants to argue that corporeal matter is not the object of our perceptions. Second, he wants to argue that it is not a substratum that underlies the sensible properties composing our perceptions.

Matter is Not the Object of Our Perceptions

Remember here that Berkeley's main point throughout is that:

(1) Whatever is perceived is immediately perceived.
(2) Only ideas are immediately perceived.
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(3) Thus, only ideas are perceived.
(4) If only ideas are perceived, we are only immediately aware of the mind's own contents
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(5) Thus, we are aware only of the mind's own contents

Hylas agrees to (1) and (2), so Philonous is always trying to show him that since this is the case, only ideas are perceived, nothing else and thus that we are aware only of the mind. Philonous's main point here is that what we have sensory knowledge of is really all in the mind. Let's look at one argument for this -- here Hylas argues that "extreme heat" must exist in the object itself, apart from the mind's awareness of it. Here's Philonous's argument against thus, arguing again that only ideas are the objects of our perceptions, not "things themselves."

(1) If something is indistinguishable from a pain, then it is a pain.
(2) A great degree of heat is indistinguishable from a pain.
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(3) So, a great degree of heat is pain.
(4) If a pain cannot exist unperceived, no great degree of heat can exist unperceived.
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(5) So, no great degree of heat can exist unperceived.
(6) If external objects are not the subject of sensations or perceptions, pains and heats cannot exist in external objects.
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(7) So, pains and heats cannot exist in external objects.
(8) Since pain exists in the mind only, heat also must exist in the mind only.

Philonous's arguments follow this sort of argumentation regularly. Some of his arguments against properties are based on an "argument from relativism";

(1) Subject A perceives property Y as Z in situation S. (A sees a thing as big)
(2) Subject B perceives property Y as Z* in situation S. (B sees the same thing as small)
(3) If the variation in subjects A and B's perceptions are explained by pointing to the cause of the perceptions, it seems that in this case one must argue that the causes are different in the same exact situation. (if we explain this by saying the cases of the perceptions are different, then the same object perceived has a cause and lacks it -- it both causes perceptions of bigness and not-bigness at the same time).
(4) Hylas explains the perceptual differences by means of postulating different causes in the same object.
(5) The same object cannot have contradictory properties in the same situation. (saying the object causes both bigness and not-bigness in the same situation is to say that the object both has an lacks a property)
(6) Hylas's explanation commits us to a contradiction.
(7) Since explaining the difference by means of extra-perceptual causes leads to a contradiction, the perceptual properties seen by A and B have real existence only in the mind.

Philonous uses this "argument from relativism" in numerous places, and he also uses it to show that there can't really be a principled distinction between what Locke calls primary and secondary properties, since the same argument works against both of them equally as well.

Matter is Not Substratum

Hylas says that matter is not the object of our perceptions, but is rather the substratum of the properties that underlie our perceptions. Philonous makes fast work of this:

(1) If X is a substratum, then X has no properties but rather is the ground of those properties).
(2) To be the ground or foundational support of properties implies that the foundation is extended.
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(3) So if X is a substratum, X is extended.
(4) If a thing is extended, that thing has at least one property (extension).
(5) If X is a substratum, then X both has no properties and X has at least one property.
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(6) So since (5) is a contradiction, substratum cannot exist (by modus tollens on 5).

Dialogue 2: Matter Plays No Explanatory Role

Berkeley's critique of matter in the first dialogue is centered around showing that our conception of matter doesn't really make any sense when it is held to scrutiny. Empiricist conception of meaning: all concepts derive from what we directly experience. At best we only experience properties, and not any underlying matter. Hence, the notion of matter has no empirical content, and is meaningless.

Esse is Percipi (To Exist is To Be Perceived)

To back up this notion, Berkeley uses, in dialogue 2, what is called the "Master Argument" to argue for esse is percipi, or the argument that "to exist is to be perceived." The argument runs like this:

(1) If X and Y can be conceptually separated, X and Y can exist separated in reality.
(2) Any conception of a state of affairs is, by definition, existing perceived by the mind.
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(3) Thus, it is not possible to conceive of a unperceived object.
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(4) Thus, it is not possible for an unperceived objcet to exist.

Now run the Master Argument against the suggestion that corporeal matter can exist unperceived:

(1) Matter can, by definition, exist unconceived.
(2) It is impossible to conceive of a material object which is unconceived of (from the Master Argument).
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(3) Thus, matter is impossible.

Next, Berkeley turns to any of Hylas's possible attempts to make sense of matter as playing some role in things. Even if he can't make sense of it as an object (it is inconceivable from dialogue 1), perhaps he can show that explanation requires that we postulate it, even if we are not sure what it is. Philonous turns to the different attempts separately.

Matter is Not a Cause

At the beginning of the Second Dialogue Hylas recounts the Lockean/Cartesian account of perception: "It is supposed the soul makes her residence in some part of the brain, from which the nerves take their rise, and are thence extended to all parts of the body: and that outward objects, by different impressions they make on the organs of sense, communicate certain vibrative motions to the nerves; and these being filled with spirits, propagate them to the brain or seat of the soul, which according to the various impressions or traces thereby made in the brain, is variously affected with ideas"

Philonous suggets that the brain is just another sensible thing, and hence is a collection of sensible qualities, which are ideas, and thus exist only in the mind. How can one of the images in our mind be said to cause all the others?

Berkeley's argument against matter in the world causing ideas or perceptions in the mind:

(1) Matter is unthinking and inactive (according to Hylas).
(2) What is inactive cannot be the cause of something active (so matter, as inactive substance, cannot be the cause of an actual perception in the mind, which is active).
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(3) Only another Mind can be the cause of our thinking.

Hylas tries, however, the explain how matter can cause perception through motion. Philonous's argument:

(1) Motion is a sensible quality
(2) If X is a sensible quality, it is an idea.
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(3) So motion is an idea.
(4) If X is an idea, X is inactive and inert.
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(5) Motion is inactive and inert.
(6) If X is inactive and inert, it cannot be the cause of what is active (by the above argument).
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(7) Motion cannot be the causes of our perception.

Notice that Philonous' position in many ways solves the problem of mind-brain interaction that Descartes faced.  For Descartes the problem (and still is the problem today!) is how to explain that seemingly unthinking stuff like neurons can produce a conscious mind. This is basically the problem Berkeley is posing. Philonous suggests that there is no causal relation between "a motion in the nerves, and the sensations of sound or color in the mind." They might always go together, but one is not the cause of the other. Berkeley solves the mind-body problem essentially by denying that bodies are different from minds.

Matter is Not an Instrument

Perhaps, Hylas says, matter is not the cause of our perceptions but rather the instrument that God (the real cause) uses to produce our perceptions. First, Philonous asks Hylas how the instrument works -- what kinds of levers or springs it utilizes so that it can function as the tool that it is. Hylas cannot say, since he has no real conception of what matter is (from the first dialogue). So Hylas says that he means it to be an instrument in a "general" way. Philonous makes quick work of this.

(1) If X is an instrument, then X is a tool used by a creature to do something that creature couldn't do without it.
(2) God uses instruments (matter) to cause perceptions.
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(3) Thus, God uses tools to do things that otherwise he wouldn't be able to do.
(4) God is omnipotent and so can do anything.
(5) (3) & (5) are together a contradiction, so one of them must be false.
(6) (4) is definitional, so (3) is false.
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(7) So God does not use matter as an instrument.

Matter is Not an Occasion

Still, Hylas wonders, couldn't matter be the occasion of our perceptions. What this means is this: God alone causes our ideas, but the presence/nonpresence of matter determines what sorts of perceptions and ideas God creates in us. In other words, matter functions as a kind of "marker" to remind God what ideas to cause in minds and when to do it.  Philonous makes quick work of this one too.

(1) If X is used as an occasion, then X is used by a creature as a sort-of "marker" or "reminder" of what to do and when.
(2) God uses matter as an occasion to create perceptions in us.
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(3) God needs markers and reminders of what to do and when.
(4) God is omniscient.
(5) If God is omniscient, he does not need markers and reminders of what to do and when.
(6) (3) and (5) are a contradiction, so one of them is false.
(7) (4) is a definition, so (3) is false.
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(8) So, matter is not an occasion.