Biff the unclean

bd-from-kg: Ah, the cogency of this argument is overpowering: "X’s argument for P is ridiculous because X also believes Q, which I think is false."

Lewis is showing more than a little hypocrisy here.
He declares thought to be irrational if it doesn't originate from an already rational source, without grounds other than he can't understand how. While (although he doesn't say it in these snippets) his idea of a "rational" source is a supernatural one who instills this intelligence by magic. Your X, P & Q argument is exactly the one Lewis is using.

Lewis was well aware of the science of the preceding 100 years.
So he was ignoring it, and mis-stating it on purpose then?
The statement is a logical deduction from the Rule that he stated earlier.
That's the sort of thing that happens when you make up your own rules and then try to impose them on reality.

Missing the point completely. Lewis is arguing that inference is itself a product of nonrational natural processes (or as he puts it, of irrational causes). Since we routinely dismiss as untrustworthy beliefs that can be fully explained as the result of irrational causes (as he illustrates in his examples), why should we trust beliefs based on inference if our belief in the reliability of inference is itself a result of irrational causes?
Because they are testable, and are show not to be irrational.
Lewis is again practicing hypocrisy. He dismisses inference while at the same time using only inference to support his wacky ideas about a completely unobservable supernatural being.

Lewis’s argument is that metaphysical naturalists also display an inordinate amount of credulity. They trust the products of their own cognitive processes when those very processes have led them to conclusions that should cause them to completely distrust them.
Stuff and nonsense. That would mean that he knew nothing of how science, or the human mind, works. He would be disregarding the fact that scientific conclusions are always tested.
For someone who is criticizing someone else’s arguments, you really need to brush up on Logic 101. Ad hominem is one of the most elementary fallacies.
I suggest that you look up what an Ad Hominem is.
I am not saying that his ideas are wrong because he is a terrible person. I'm saying that he appears to be misrepresenting himself. His ideas stand or fall on their own merit.

Anyway, anyone familiar with Lewis’s writings would know that he gave a detailed account of his conversion from atheism in Surprised by Joy. Are you seriously claiming that this entire book is a big fat lie?
You cannot turn on the AM radio in your car without being assaulted by religious hucksters, a goodly percentage of whom claim to have once been Atheists before they were "saved." Most don't even know what an Atheist is, but all of them are happy to send you their book…for a "faith offering" of course.

… before rejecting an argument it’s a good idea to get some idea of what the argument is and what it is about it that makes a number of very intelligent people take it seriously.
Since there are as many letters following my name as you will find in an average Campbell's Alphabet Soup can I am confident enough of my own intelligence. I am quite bright enough to recognize baloney when I see it…even if it comes from England…and am not impressed by these unnamed very intelligent people who cannot.

bd-from-kg

Steven Carr:

He would be wrong if he had said any such thing. Why don’t you try quoting what he actually said? That would at least make it a little harder to grossly misrepresent him.

Yes, I seem to be overlooking it completely. I can’t find it anywhere.

No one takes it as a general rule that nothing can have property X unless it is caused by something that has property X. If Lewis were relying on such a rule his argument would indeed be complete hogwash. He isn’t even arguing that a thought cannot be rational unless it has rational causes. He’s arguing basically that you’re not rationally justified in continuing to believe something once you realize that the belief is entirely the product of nonrational causes.

Could you please give me a hint as to what you’re talking about here? Please quote the passage in which you think he “compares the state of scientific reasoning with the thoughts of just one person”.

Gunnaheave

Bd:

1) You said; "Lewis didn’t even use the term “credibility”."

My use of 'credibility' was a loose paraphrase of… "Both sentences explain why the man thinks as he does. But the one explanation substantiates the value of his thought, the other wholly discredits it."

Close enough in my book, but if my shift of vocabulary is off in any relevant manner, then feel free to point it out.

2) You said; "But of course a statement is discredited if it is learned that the person who made it had no rational justification whatever for believing it."

There is an ambiguity here. If by 'discredited' you mean that it lacks support you are correct; if by 'discredited' you mean that it is shown to be wrong, then no it is not. You subsequent comments indicate that you are aware of this difference, but Lewis' argument appears to assume the stronger sense of discredited insofar as he is asserting the statements are shown to be wrong. See; "We may in fact state it as a rule that no thought is valid if it can be fully explained as the result of irrational causes." This indicates that Lewis is not merely inferring a lack of support for the initial claim; he is actually inferring a substantial negation of the proposition from the mere lack of support. Here he even elevates this to a principle of reason, but it is one that effectively reverses the significants of logical support.

3) You said; "If by “valid” Lewis had meant “true”, you’d be right. But obviously what he meant by “valid” was something like “rational” or “rationally justified” (depending on whether one is talking about the process leading to the belief or the belief itself). "

Actually since he is talking about the validity of the 'thought' he has fudged the issue, and since it is the original claim that is said to be discredity, then no he is not referring to the inferences used to justify it. He is trying to fuse the evaluation of inference validities with that f statements, and it is introducing more precision into the argument than he intended to try and say that while referring to an initial claim as being invalid or discredited he is actually referring to an argument offered in support of it.

4) As to the final point, evaluating a 'cause' of a thought process has no logical relationship to the process of logical evaluation. This gets to the heart of the matter. Lewis would regard a belief as discredited if the thought process that lead to it was irrational, but this substitutes a psychoogical inquiry for a logical one. Just because logicians and psychologists both speak of rationality doesn't mean that they are really talking about the same thing. This is simply another equivocation.

bd-from-kg

ReasonableDoubt:

Do you concede, then, that there is no rational justification for your belief that your beliefs “work” in a pragmatic sense? Maybe our belief that they do is part of the huge delusion. And I don’t know about you, but I do care whether my beliefs are actually true – not merely whether they “work”.

IMHO, it doesn’t, although Lewis naturally goes on to argue that it does. But I don’t want to play Devil’s advocate on this point as well. I have my hands full playing Devil’s advocate on the original point.

Llyricist

Lewis stated that if you follow his rule with any particular thought, you must follow it for all thoughts collectively, then he magically asserted "that is, Human reason as a whole".

human reason != thought, not in the sense that he is using these terms when he defined his rule. You only have a valid "thought" when the "reasoning" applied or used to arrive at that "thought" is rational. Therefore, "reason" PRECEDES "thought", and is NOT the same thing. Since it is not the same thing, you cannot apply the same rules to it. In fact, how do you apply reason to validate itself? He's saying the tool used to determine rationality has to have a rational reason. (my head hurts)

Basically "reason" is just an understanding of cause and effect, and there is no valid reason to assume that understanding has any "rational" basis beyond simple survival. More complex reasoning can evolve using the basic reason, but the basic cause and effect relationship is the bedrock foundation.

And his arguments regarding inference is rubbish too, it HAS been observed and IS observed by everybody every day, no inference necessary.

And his final argument is the kind of argument that, when taken to full effect, "undoes" existence, which personally, I have no use for. Ya gotta stop that line of argument somewhere, he chooses to veer off into theism, I choose to stop at the understanding of cause and effect brought about by evolution.

bd-from-kg

Steven Carr:

Huh? Of course heredity cannot be directly observed; we know about it only through inference.

Elimination of a particular tadpole could be observed directly, though it rarely is. But what Lewis is obviously talking about is natural selection, which clearly has to be inferred. And the “struggle for existence” is a generalization based on a great many observations and inferences from them.

Frankly, you seem to have a greatly exaggerated sense of what can be observed. And even our interpretation of what we observe depends heavily on inference. Thus, in the ordinary way I might say that I “observed” my neighbor leaving for work at 7:45. But did I? What I really observed was my neighbor leaving his house, getting into his car, and driving in a particular direction. I inferred from this that he was leaving for work. And for that matter, how do I know that that was my neighbor leaving that house? Well, that’s the conclusion of a long string of (largely subconscious) inferences from the images that appeared on my retina. In reality very little of what we “know” is directly observed; at least 99.9% of it is inferred.

But I’m not sure what you think any of this has to do with Lewis’s argument.

The ad hominems just keep coming, don’t they? Why not try sticking to actual arguments?

Biff the unclean

You really have to look up what the term "ad hominems" means.
Carr is not making an ad hominem, he is calling a spade a spade. He isn't judging the response by the character of the man. He is judging the man by the character of the response.

bd-from-kg

Biff the unclean
I know perfectly well what ad hominem means. It means attacking the person presenting an argument instead of the argument itself. The idea is to discredit the argument by discrediting the person presenting it. SC was suggesting that Lewis thought other people were irrational because he realized that he was. No meant to be taken literally, no doubt, but the idea is to plant a negative image of Lewis in the reader's mind. If that isn't an ad hominem argument there's no such thing.

A personal attack is OK if the argument is about is the character of the person in question, or if his personal testimony is being offered as evidence. It's totally inappropriate in most other circumstances.

Someone with as many letters following his name as you will find in an average Campbell's Alphabet Soup can should know that. If you tried to publish an article containing this kind of personal attack in a scholarly journal it would be rejected without hesitation. Surely you understand the reasons for this?

Volker

Ah, those weak analogies - and I haven't improved on this, only made it worse. My apologies.

The orignal argument, as I understand it, goes as this (in my own words):

(P1) You can't base your belief or your thinking on irrational grounds. Otherwise, your thinking will be irrational, too.
(P2) Nature doesn't depend on or is based on rational thinking.
(C) If you think your thinking ist completely based on nature, it is irrational.

Hope this makes it clearer. Clearly, either (P1) or (P2) (or both) must be false, otherwise you've just stated that your thinking isn't rational. Lewis arguments now against premise (P2). I've argued that the logic isn't false, but that (P1) is false, not (P2).

Let me cite Dawkins to explain why (P2) fails:

"Science offers us an explanation of how complexity (the difficult) arose
out of simplicity (the easy). The hypothesis of God offers no worthwhile
explanation for anything, for it simply postulates what we are trying to
explain. It postulates the difficult to explain, and leaves it at that.
We cannot prove that there is no God, but we can safely conclude the He
is very, very improbable indeed."
(Richard Dawkins, from the _New Humanist_, the Journal of the Rationalist Press Association, Vol 107 No 2)

I think, Lewis has found a very clever argument. bd_from_kg admits this, too, and I've to admit that I'm a fan of bd_from_kg (my website about atheism - Atheismus Online, unfortunately in german language, starts with an argument I've learned from him - Bayes theorem).

I think most of you underestimate Lewis. That is far more dangerous than to overestimate him.

bd-from-kg

Biff the unclean:

Another ad hominem. Don’t you ever get tired of this stuff? 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. (And even then you shouldn’t do it unless it’s relevant to the debate.) You throw out such charges at the drop of a hat.

No. His argument is that you’re not rationally justified in continuing to believe something once you realize that the belief is entirely the product of nonrational causes. The belief might be rationally justified, but you’re not justified in believing that it is.

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.

The problem is that this “showing” also involves inference. So this demonstration of the reliability of inference is circular.

Yet another ad hominem . You just can’t help yourself, can you?

Anyway, Lewis does not dismiss inference. What he 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.

Do you know anything at all about Lewis? 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”. 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. In any case, his argument doesn’t depend in the least on any details about how the human mind works, whether it’s doing science or something else. 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.

Incredible. This comment was prompted by my response to this:

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?

Comparing Lewis to such people is simply grotesque. Suggesting that he lied about his conversion from atheism to Christianity is so absurd that it can only be chalked up to ignorance. And do you still say that you’re not engaging in ad hominem attacks on Lewis’s credibility? Perhaps, then, you’ll be kind enough to explain the relevance of these comments to his argument. Why are you trying to direct our attention to supposed flaws in Lewis’s character rather than flaws in his argument?

I’m not questioning your intelligence. I do have some doubts about your modesty though.

I’m impressed. Sometimes I have to think about an argument to figure out that it’s baloney.

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.