Russell's Argument for Matter and Criticism of Berkeley's Idealism

Before reading this post it is recommended but not necessary that you read the prior post on Berkeley since, in the first part, Russell is responding to his arguments.

Introduction and Context
Russell is doing two things in Ch. 2 of The Problems of Philosophy.  The overall project can be viewed as a proposed solution to Descartes' skepticism: i.e, how can we know that our perceptions of the world match up with what it is actually like.   Within that context he (1) argues for the existence of mind-independent entities (i.e., composed of matter) that are responsible for our perceptions and (2) gives some reasons for which we should reject Berkeley's solution (idealism).

We can distinguish between Berkeley and Russell by their answers to the second of following two questions: When I look at the table in front of me (A) is the table real? and (B) what sort of object is it?  While they both agree that the table is real, they disagree as to the answer of (2):  Berkeley thinks the table is a collection of ideas in the mind of God while Russell says it is a physical object composed of matter.  

It's important to note one more point of agreement: they both agree that the sense data ("ideas" in Berkeley-language) are real--regardless of whether they be the product of perception, imagination, dreams, or memory. The issue of contention is in regards to the nature of the thing causing us to perceive sense data.

Before proceeding, just a quick note about Berkeley's "mind of God" stuff.  We might be tempted to dismiss his argument because it depends on (what many philosophers think is) a dubious assumption or, at least, that it is not an assumption we should grant without proof or argument.   But we don't need to postulate God for his argument to work.  We can easily replace God with the more modern "Matrix" and we can say all ideas are simply code in the Matrix program.  Check out "the simulation argument" for elaboration on this topic.

http://www.simulation-argument.com/

Why The Nature of the Table Matters, The Problem of Solipsism, and the Zombie Apocalypse
All this talk about whether the table is material or a collection of ideas seems pretty wack.  And why should we care anyway?  What hangs on it?  Whether there are mind-independent objects matters because if the answer is "no," then there doesn't seem to be any way to know that other people exist.

Lets break that down:  If we suppose that there aren't mind-independent material bodies (or that we can't know about them), then how in tarnation can I know if there are other people with minds (i.e., that are conscious) in the world?  If the only thing I can perceive and know to exist are my own thoughts, then I can never get out of my own head to verify if the objects-that-look-like-people around me are conscious.  I might be the only person in the universe capable of mental activity (sometimes I have my suspicions when I'm on the strip...don't get me started...).

Otherwise stated, if we adopt Berkeley's hypothesis, there is no external world of things, the only real things are sense data in my mind. Other "people" might merely be clusters of properties (ideas/sense data of things that resemble bodies) in God's mind that I'm perceiving.  If so, it doesn't seem like there's any way for me to verify if they have independent minds.  Maybe they're just sims that are programed by God to act as though they have minds-- or worse, maybe I'm living in the zombie apocalypse and they're coming for my mind! (Thankfully twinkies are back on the market...)

1st Argument Vs Idealism:  The Tablecloth and the Argument from Common Sense
Berkeley argues that in order for something to exist, it has to be perceived.  Russell presents the following situation to demonstrate why we should reject Berkeley's position:

(P1)  If you're looking at a table by both accounts (i.e., materialist and idealist) the table exists.
(P2)  Now, suppose we cover the table with a tablecloth. We no longer perceive the table, only the tablecloth which is in the shape of a table.
(P3)  If perception is required for existence, then according to idealism, the covered table no longer exists because it isn't being perceived--only the tablecloth is.  
(P4)  P3 is wack and flies in the face of common sense. Surely, the table is still there.
(C)  Therefore, idealism is wack and we should reject it.

2nd Argument Vs Idealism:  Public Objects
Simply because something conflicts with our common sense is not a reason to completely reject it and consider it invalid. If all we wanted to do was figure out what common sense tells us, we'd be experimental psychologists, not philosophers.  We're going to need another argument for external objects:

If 10 people are sitting around a table, the sense data for that table are private for each person.  That is, each person has a slightly different idea of a table (because of slightly different points of view).  According to Berkeley, this would mean there are 10 different tables because ideas are all particular things and are not caused by any external object. (10 different sets of ideas=10 different objects.)  

But this is loco.  Surely everyone is seeing the the same table.  It makes way more sense to say there is only one external table, and that the 10 people are all perceiving that same table from different points of view. This is the only way that there could be public neutral objects. Therefore, since idealism doesn't give us (a probable) account of public objects, it must be false and material objects exist.

Lets summarize that: 
The fact that 10 people can look at a table (for example) from different perspectives and see something that is mostly similar is good evidence for a material table.  The differences in perspective can be accounted for via the laws of perspective and reflection of light rather than saying they're all seeing a different table.

Philosophy Challenge:  Consider how Berkeley might respond.

Problem of Circularity A skeptic might respond to Russell by accusing him of assuming in his argument the very thing he is trying to prove:  that external material objects exist.  Russell's argument assumes the existence of other people which are, after all, external objects.  He infers the other people's existence based on his sense data!  But that's no proof of their independent material existence, it is only proof of the existence sense data that have the appearance of other people.

Back to the drawing board...

Ok, we're going to have to make some concessions:
1.  No logical absurdity results from the hypothesis that the world consists of myself and my thoughts and feelings and sensations, and that everything else is mere fancy.
2.  No logical possibility results in the supposition that the whole of life is a dream, in which we ourselves create all the objects that come before us.

Damn!  Now what?

Oh...wait...

Hold on a tick...

By jove! I think Russell's got it!

Appeal to Probability:  Just because 1 and 2 are not logically impossible, this is no reason to suppose that they are true. Logical possibility doesn't imply truth, nor does it imply plausibly true--it only tells us what is logically possible!  Ok, back in business...

Argument from Simplicity:  The Cat 
Suppose Berkeley is right and the only things that are real are sense-data and that things don't exist when we don't perceive them.  How then are we to explain the movement of my cat?  When I looked at it a minute ago it was in one part of the room.  Looking up from my desk, now I see it's on the other side of the room.  

If it didn't exist when I wasn't perceiving it, how did it get from one side of the room to the other?  Is there a mini-transporter the cat's using that I don't know about?  It seems much more plausible that the cat exists and persists as an external object and walked across the room.

Consider how we might account for the cat's hunger.  I saw him in the morning and at night the next time I saw him, he was hungry.  If the cat only exists as sense data when I perceive him, then he didn't exist in the intermediary and it seems peculiar that he is hungry now.  If, however, we posit mind-independent entities, why the cat gets hungry (or at least displays the behaviours of hunger) seems to make a lot more sense.  And how do collections of sense data get hungry?

Now apply this same argument to the complex actions and behaviours of humans...Positing mind-independent entities give a much simpler account of our world.

Argument from Instinct and the Job of Philosophy:
Admittedly, the arguments from public objects and from simplicity are not unassailable but their conclusions align most closely with our instincts.  We can still apply to them the method of Cartesian doubt.  However, "all knowledge, we find, must be built up upon our instinctive beliefs, and if these are rejected, nothing is left."  

Of course, some instincts are stronger than others and some "become entangled with other beliefs" that aren't really instinctive (although because of habit we might suppose them to be).   Nevertheless, it is the job of philosophy to untangle and systematize our different instinctive beliefs and ensure that our most fundamental ones don't contradict each other.  Coherence won't guarantee truth but it gives us a better chance than having a collection of mutually exclusive beliefs.

The bottom line is this:  We can never completely overcome Cartesian doubt.  We may be in a dream world, or in the Matrix.  It's possible.  But if we order our beliefs in terms of probability and reject those that are inconsistent with those that we consider to be most probable, then we can have something like knowledge.  The degree to which we can order our beliefs and ensure that they are coherent and in harmony is the degree to which we can say we have knowledge...and this is the philosopher's job.

Philosophy Challenge:  Russell's theory of knowledge is essentially a coherentist proposal.  What objections can you come up with?