Many of his comments are obvious, but always worth keeping in mind...

'Another kind of diversion is the trick of fastening on a trivial point in an opponent's argument, defeating him on that , and then leaving it to be supposed that he has been defeated on the main question...'

Detailed discussion is, in my view, too often an excuse for not seeing the broader issues at stake. Things that are obvious are just as worth stating clearly as the detailed but obscure point that shows the speaker's erudition.

Thouless offers many good examples of unsound arguments. Here, for example is an extract, which starts with an argument about belief in the survival of death:

... we cannot prove a conclusion by an unsound form of argument based on true premises. Let us, for example, consider the following argument:

'The delusions which mislead men arise from their tendency to believe that to be true which corresponds to their wishes. One of the strong desires that affect human belief is the hope that man will escape extinction at death and live eternally in some ideal haven of bliss. No one who has any understanding of the origin of delusional systems in human wishes can fail to conclude that this belief in immortality is a delusion.'

Again, we may be uncertain whether or not this is a sound argument both because it deals with a matter on which we are inclined to feel strongly and also because the structure of the argument is concealed by a lot of words. But, if we reduce it to a simple form it becomes:

        Delusions are beliefs in what we wish to be true.

        Belief in immortality is a belief in what we wish to be true.

        Therefore, belief in immortality is a delusion.

or, in an A, B, C symbolism:

        All As are B

        C is a B

        Therefore C is an A.

That this argument is unsound is clear if we replace it by a trivial example with true premises which leads to an obviously false conclusion:

        All cats are four-legged animals.

        All dogs are four-legged animals.

        Therefore all dogs are cats.

Here's the belated January extract,  perhaps it caught my eye because of the current inquiry into the Iraq war, or the marking of one year of Obama's presidency... Whatever, it is taken from his chapter on the problems of definition (1990 edition):

Definition is a process intended to make our thought clear and our speech understandable to others. The use of definition as a means of indicating opinions or valuation defeats its proper aim. Governments are no more immune that individuals to this fatuous use of language. In 1986 the US government announced that it reserved the right to use for military purposes a space station which was to be jointly paid for by America and her European allies. It was thought that there might be a hostile response from the allies who had believed that the station was only to be used for 'peaceful' purposes. An Air Force official said that other countries might have misinterpreted a policy of restricting space ventures to 'peaceful purposes' as meaning non-military. 'We will limit our use of outer space for peaceful purposes,' he said. 'Our philosophy is that anything the United States does, including the Department of Defence, is in the name of peace...' I hardly need to point out that the Soviet government, and indeed any other government in the world, could make the same claim, but that would not make them any less likely to become involved in armed conflict. (from p42)

A rather dated example (but hopefully, if the book goes to a new edition, examples will be replaced, as happened before), but making a point - and an example of the way in which Thouless deals with everything with an easy style and a shrewd eye for examples of crooked thinking.

Here's the December 09 extract, on the law of the excluded middle and the property of continuous variation...

There is an old law of logic called the 'Law of the Excluded Middle'. which says that A is either B or not B. Thus a piece of paper is either white or not white. There is a sense in which this is obviously true, yet the  kind of thinking that it leads to can be dangerous and misleading when applied to the real world...

In human life we find properties which show continuous variation, and (just as in the case of black and white) we find this property obscured by the use of words implying sharp distinctions. 'Sane' and 'insane', 'good' and 'bad', and 'intelligent' and 'unintelligent' are pairs of opposites which show this property of continuous variation. Our use of two sharply contrasted terms 'sane' of ourselves and our neighbours and 'insane' of those unfortunate people confined in mental hospitals leads is to forget the continuity between them. The essential difference between those we call sane and those we call insane is simply the degree to which they are able to adapt themselves to their environments...

A speaker may claim that is it impossible for there to be any such thing as a non-aligned state by saying 'A country can either be pro-Western or anti-Western'...

All arguments that say@'An X must be either Y or not-Y' must be treated as unsound if Y is a characteristic that shows continuous variation...

(from pages 34 and 36 of the 1990 edition)

Here's a thought for November 09, on the choice of words...

'When we become aware of [the] difference between the factual and the emotional use of words, we notice that words which carry more or less strong suggestions of emotional attitudes are very common and are ordinarily used in discussion of such controversial questions as those of politics, morals and religion. This is one reason why people can go on discussing such questions without getting much nearer to a rational solution of them.

'There is a well-known saying that the word 'firm' can be declines as follows: I am firm, you are obstinate, he is pig-headed. This is a simply illustration of what is meant. 'Firm', 'obstinate' and 'pig-headed' all have the same factual meaning - that is, following one's own course of action and refusing to be influenced by other people's opinions...   If we wanted to find an emotionally neutral term that would convey the same idea without expressing either approval or disapproval, we should say perhaps 'X is not easily influenced'.

...

'Such words are, no doubt useful but they are a danger to reasonable thinking. A particular case which is widely used today is the word 'guerrilla'. One might decline this word in the following way: I am a freedom fighter, you are a guerrilla; he is a terrorist.

 (from page 3 of the 1990 edition)

Obvious enough, perhaps, but one only has to reflect on reports from Afghanistan about insurgents, or consider how one staunchly staunchly religious person may become a martyr, another branded a dangerous fanatic, to feel a Thouless-induced irritation at half of what appears in the papers.