Jobar

bd, Biff- certainly you are both entitled to your own opinions about Lewis, and to disagree with each others'. But please, try to keep your disagreements civil. Remember that making someone angry is not a good way to convince him that you are right.

bd-from-kg

Gunnaheave:

Why do you continue to cling to this misinterpretation when I’ve already corrected it? In any case, the principle of charitable interpretation should have led you to interpret “valid” as meaning something like “rationally justified” for the simple reason that the statement is nonsensical if “valid” is interpreted as “true”.

What Lewis is arguing is that (if we assume MN) we are not rationally justified in trusting our cognitive faculties to be reliable, meaning that there is no justification for supposing that they reliably produce true beliefs (even when we’re not being misled). Among other things, this means that we are not rationally justified in assuming that our cognitive processes tend to be truth-preserving – that given true inputs they tend to produce true outputs. So he’s not “fudging”, at all; he includes both the inferences (i.e., the cognitive process) leading to our beliefs and the beliefs themselves.

It seems to me that you want to argue in a circle. You want to say that we can verify that our cognitive faculties are generally reliable (i.e., reliably produce true beliefs) by analyzing either the cognitive processes themselves or their “outputs” using those very cognitive faculties. This is rather like saying that we can determine whether a measuring device is malfunctioning by using it to “measure itself”. Surely it’s clear that you can’t verify that your own thought processes are truth-preserving by using those very thought processes to produce the belief “My thought processes are truth-preserving”? If your thought processes are truth-preserving, of course, all is well, but if they aren’t there is no more reason to trust this particular output more than you’d trust any other. It’s like concluding that someone is telling the truth because he says he is.

But we do this all the time. That’s Lewis’s point. The minute we realize that a belief has nonrational causes we disregard it. And this is true even of our own beliefs.

Actually this is neither a psychological nor a logical inquiry. It’s a philosophical one. Specifically, it’s the question of whether we are ever rationally justified in continuing to believe something one we recognize that the belief can be traced entirely to nonrational causes.

An argument can be perfectly logical, but unless we are rationally justified in believing that it’s logical we are not rationally justified in believing the conclusion. For example, suppose that you knew nothing about model theory and someone presented you with an alleged proof of the independence of the continuum hypothesis (which is in fact, unknown to you, Cohen’s proof). Now suppose that you’ve memorized the proof. I guarantee that you wouldn’t understand it. Now let’s further suppose that you have no idea whether this result is generally thought (by competent mathematicians) to be true or whether the person who presented you with it is to be trusted, so you have no rational grounds to believe that this is a valid proof, or that the conclusion is a valid theorem. So here you know a completely sound, valid argument leading to a correct conclusion, but you are not rationally justified in believing that conclusion, or that the inferences leading to it are valid.

This is a reasonably good analogy to the situation that Lewis is saying we’re in with respect to all of our beliefs if we accept MN.

That’s certainly true. In fact, I’m not aware that logicians as such talk about rationality at all. They talk about things like validly and consistency. Anyway, we’re not talking about “rationality” per se but about rational justification, which is a philosophical concept. The doubt that Lewis is raising is the kind often referred to as a “philosopher’s doubt”. Obviously no sane person really doubts that our cognitive processes are reliable. He’s asking whether, in the final analysis, metaphysical naturalists are rationally justified in so believing.

bd-from-kg

Jobar
Absolutely. That's the basic reason why ad hominem attacks are considered out of place in serious discussions. They get in the way of rational discourse.

Anyway, don't worry. If BTU continues along these lines I won't be replying to him in the future.

Llyricist

And in this question he is FAR from original, I believe it's generally a given that we can't have 100% certainty that we exist at all. But so far the use for this idea is restricted to fodder for movies like The Matrix as far as I can tell. (and arguments for philosophers , as long as they don't build "Deep Thought")

bd-from-kg

Llyricist :

Well, yes. That’s a basic rule of logic: if P(x) is true for any given x, then “For all x, P(x)” is true.

Yes indeed. And if the cognitive faculties that produce what we think of as “reasoning” are purely the product of nonrational causes, what rational justification do we have for thinking that our thoughts are rational – or in other words, that what we think of as “reasoning” really is “reasoning”?

Um, not really.

And what rational basis do we have for assuming that our cognitive processes tend to be “survival-enhancing”? The outputs of those very cognitive processes? And supposing that this is true, what rational reason do we have for supposing that the cognitive processes that tend to be “survival-enhancing” are the very ones that reliably produce true beliefs? This seems to be, at best, a very “downstream” product of these same cognitive processes – in other words, the conclusion of a very long string of inferences, which we must be rationally justified in trusting to be valid in order to be rationally justified in believing the conclusion.

In general the correctness of our inferences isn’t observed, it’s inferred from observations. Moreover, the conclusion that because our inferences have yielded correct predictions in the past they will do so in the future is based on yet another inference.

In other words, you reject the argument because you don’t like the conclusion. This is the fallacy of “Appeal to Consequences”.

P.S. Re your latest post: the question of whether one is rationally justified in believing something is quite different from the question of whether one knows it, much less whether one knows it with certainty. Pretty much all philosophers agree that we can’t know with certainty that we’re not in the Matrix, and some would even go so far as to say that we can’t know that we’re not in the Matrix at all (depending on just what they mean by “knowing”). But almost all would agree that we’re rationally justified in believing that we’re not in the Matrix. Lewis’s argument is about rational justification, not the possibility of “knowing with certainty”.

And by the way, to the best of my knowledge Lewis’s argument was pretty original at the time he came up with it. Since then it’s been “refined and extended”, but he seems to have been the original author. But I could be wrong.

Llyricist

Congratulations, you just proved that there is NO rational justification for ANYTHING.

I'd like to know your definition of rational and non-rational. Lewis seems pretty clear in his examples that irrational means a thought arrived at with faulty reasoning, whether it's a Logical fallacy, as in the black dog example, or errors in perception as in the drunk example, or psycho-physical problems evoking an emotional "reason". In no case did he give an example of a thought arrived at with no reason at all, in fact he GAVE the reasons. So in his introduction he is describing the difference between "good reasoning" (rational) and "faulty reasoning" (irrational), nowhere did he bring up the idea of non-rational. And he certainly didn't give any examples.

You seem to think that reason isn't based on the understanding of cause and effect?? pray tell, what the heck IS it based on???

anyhow how can nature be considered to be irrational given the way LEWIS illustrated the concept? I certainly don't think nature does anything using faulty reasoning , so actually I don't believe our ability to think rationally is based on "irrational" causes, at least not as described by Lewis.

Biff the unclean

BFK: Another ad hominem.
Not at all. You really don't understand what an ad hominem is, I'll try to explain. It is an attempt to refute an unrelated argument by attacking the persons character. A classic example is that by pointing out that Darwin was a racist many Creationists discredit Natural Selection.

Have you ever heard of elementary courtesy? One does not accuse one’s opponents of low motives or dishonesty unless one has some serious evidence of it.
Since I was talking about Lewis using arguments to discredit opposing views that equally discredited his own while ignoring them in relation to his own…what else does one call this than hypocrisy?
You seem to think that Lewis is owed some reverence?

The belief might be rationally justified, but you’re not justified in believing that it is.
An argument that applies at least as well, if not better, to the contentions of supernaturalism that Lewis himself makes.

Whether Lewis is right about what metaphysical naturalism implies about whether we are rationally justified in believing our cognitive faculties to be reliable is independent of whether God exists or whether presupposing that God exists is a solution to the problem (if there is a problem). Let’s try to stay focused.
Focus is what I am trying to promote. Lewis is trying to lead the reader to abandon naturalism in favor of supernaturalism with claims that the natural isn't rational.

The problem is that this "showing" also involves inference. So this demonstration of the reliability of inference is circular.
Not really, because one inference is tested against multiple inferences. Since inference is testable, it is useable.
Lewis wishes to discredit and discard the testable so that he will feel free to embrace the un-testable.

(What) Lewis … says is that the metaphysical naturalist is not justified in trusting inference because his underlying assumptions imply that his own cognitive faculties are not reliable.
A classic strawman.
Do you know anything at all about Lewis?
I've read several of his books and have seen the recent BBC biography on him.

This is an accurate representation of his argument, and he was as familiar as any intelligent, well-read layman with the science of his day and with "how science works".
Then that leads us to a worse problem. If he was not uninformed about how science works then the only other contingent is that he was being less than truthful.

He was, after all, a don at Oxford and later at Cambridge, and participated actively for decades in debates with people who were very knowledgeable indeed in these areas.
Then why does he write as if he had not?

It depends only on the fact that the human brain (according to MN) is entirely the product of "blind" (i.e., nonrational) natural laws and is controlled entirely by those same laws.
Which is a misrepresentation of the facts, as has been pointed out several times by others in this thread.

So let’s see. You introduce the completely irrelevant fact that Lewis "claims" to have once been an atheist, then call this a "big fat lie", but deny that this was an ad hominem attack. Are you serious?
Yes, because this points towards motives behind Lewis' claims

Comparing Lewis to such people (radio religious hucksters) is simply grotesque.
If it quacks like a duck, and it waddles like a duck…

Suggesting that he lied about his conversion from atheism to Christianity is so absurd that it can only be chalked up to ignorance.
No, it can be chalked up to reading Mere Christianity and seeing his step- sons interview

Why are you trying to direct our attention to supposed flaws in Lewis’s character rather than flaws in his argument?
He was the one who included his "conversion" as part of his argument in his writings. It can't be foul for me if it's fair for him.

I’m not questioning your intelligence. I do have some doubts about your modesty though.
I must apologize for that Campbell's soup remark. I added it with the sole purpose of getting a rise out of you, sorry. It's just that I find a great deal of amusement in Xian braggadocio claims of their humbleness. Any suggestion that a person might actually be adequate is met with near hysteria.

It’s depressing that the greater part of this post has had to be devoted to stuff unrelated to Lewis’s argument. If this continues I’m going to have to stop replying to your posts. I don’t have time for this.
It's a shame that you accept Lewis as an authority without applying any skepticism to what he writes or to his tortured logic. I have plenty of time and fully intend to reply to your posts, you may do as you please.

Llyricist

btw bd,

Don't think I didn't notice that you skipped right over my main objection to Lewis' line of reasoning in your reply i.e. all thoughts collectively is NOT the same as human reason as a whole, not the way HE described "thoughts" in THIS argument as posted here in this thread.

If he makes the arguments YOU are attributing to him elsewhere, it would be helpful if you posted the relevant quotes.

Otherwise you should take credit for improving on his arguments, but first you must bridge the gap between his idea of irrational thought and your idea of non rational causes.

Llyricist

I didn' reject the argument, I said I have no use for it, you can argue it all day among other philosophers or pot smokers, I've been there and done that myself, and found it not the least bit productive and only gratifying for a while. Better for me just to accept some level of "reality" and live my life.

Vorkosigan

'If the solar system was brought about by an accidental collision, then the appearance of organic life on this planet was also an accident, and the whole evolution of Man was an accident too. If so, then all our thought processes are mere accidents - the accidental by-product of the movement of atoms. And this holds for the materialists and astronomers as well as for anyone else's. But if their thoughts ?i.e. of Materialism and astronomy ?are merely accidental by-products, why should we believe them to be true? I see no reason for believing that one accident should be able to give a correct account of all the other accidents.'

C'mon, there's no depth at all to this "argument" -- and there I slander the good name of many philosophers by so terming this heap of non sequitors. And the "clarifying paragraph" that BD put up is even more silly.

Now it would clearly be preposterous to apply this rule to each particular thought as we come to it and yet not apply it to all thoughts taken collectively, that is, to human reason as a whole. Each particular thought is valueless if it is the result of irrational causes. Obviously, then, the whole process of human thought, what we call Reason, is equally valueless if it is the result of irrational causes. Hence every theory of the universe which makes the human mind a result of irrational causes is inadmissible, for it would be a proof that there are no such things as proof. Which is nonsense.

It is classic Lewis, sliding together two different meanings of the word "irrational" together and the slipping into the other one hoping the reader won't notice. There's no depth here at all, BD. I'm a little suprised you are defending low-level crap like this.

Even then you cannot show that our processes of thought yield truth unless you are allowed to argue “Because a thought is useful, therefore it must be (at least partly) true.?But this is itself an inference. If you trust it, you are once more assuming that very validity which you set out to prove.

There's too much Bad Thinking going on here to really get into this, but one might note in passing that Lewis does not here explain what he means by Truth. Does he give us a definition somewhere else.

Vorkosigan