Detecting illogical reasoning
and weak argumentation

As a critical reader, you need to be able to recognise and analyse instances of illogical reasoning and weak argumentation.  A critical reader needs to be able to detect writers trying to disguise weak content by the clever use of argumentative form, purely to persuade the reader of the validity of their argument.
Here are some common uses of illogical reasoning and weak argumentation.

Straw Arguments

This is the most common type of weak argument.

Straw lacks substance, it blows away in the wind. A straw argument is therefore a fragile one, that is easy to demolish.

Here are some ways in which straw arguments are made:

If you carefully question whether someone opposing a position/argument/theory is presenting an fair and accurate account, then you will not be deceived by straw arguments.

If, in your own argumentation, you fail to cite strong or representative versions of the arguments you are opposing, you will be suspected of presenting a straw argument.

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Circular arguments

If you are told you have made a circular argument, you have given the impression that you are saying something meaningful and logical, when in fact you are not.

This involves drawing a conclusion from a premise (baseline principle or assumption) which is itself dependent on what is asserted in the conclusion. In other words, you are not actually proving anything.

For example, it may be argued that money is the root of all evil because money is the cause of all human misery and wickedness. Or one may say:

  • Walter Scott is certainly a better writer than Jane Austen. I know this because my teacher who is an expert told me so. I am sure my teacher is an expert! Who other than an expert would be qualified to compare Scott to Austen?
  • The circularity of the argument in these examples is obvious. But it is often hard to detect when the circle of the argument is a big one.

    An argument of this type may extend over a long article or even a book.

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    False analogies

    Like a circular argument, a false analogy proves nothing.

    In a false analogy, there is only a superficial or chance similarity between the things that are compared; a small degree of similarity may be used to give the impression that the things are almost identical.

    An advertisement may, for example, read as follows:

  • John Lee aimed high. So he took our Made-simple Business Management Course. Now he is the Director of a big money-making enterprise, and he lives happily with his beautiful wife and children in a luxurious sea-side bungalow. You too must aim high! Remember: what Mr. John Lee has achieved, you also can!
  • If you read the advertisement carefully, you can see that even if the John referred to in the advertisement does really exist, readers also "aiming high" might lack other crucial characteristics which contributed to John Lee’s success: e.g. his keen interest and aptitude, financial backing or business luck.

    These might all have been more important reasons for his success than following up that advertisement.

    When you come across an analogy in an argument, make sure that the things compared share the characteristics that are relevant to the conclusion.

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    Either-or assumptions

    This type of reasoning is also weak, based on the assumption that there is no middle ground between two extremes: things are either black or white, right or wrong!

    For example, a candidate standing in a political election might say:

  • It is common knowledge that my opponent is not quite normal in his behaviour. How then, my friends, can we entrust an abnormal person with heavy responsibilities?
  • The problem here is the assumption that there are only two options - black or white.

    But reality extends across a spectrum. Between the extreme states of normality and abnormality are varying degrees of normality.

    When something is not black, it need not necessarily be white. It could be of many different shades of grey.

    This is similar to the straw argument, where an extreme, barely tenable position is attributed to someone, in order to persuade others to take your side.

    For example:
    If so many people do it, it must be right/good.

    A fashion designer could try to promote a particular style of dress like this:

  • Wearing the See-through Ultra-mini is certainly not immoral, because most women like it. Large numbers of such dresses are sold every day!
  • Although the argument appears to be persuasive, it is important to remember that people are often more easily persuaded by majority attitudes or behaviour , by the consensus, than by reason.

    The fact that many people smoke cigarettes does not mean that smoking is good.

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    Jumping to Unjustified Conclusions

    To be able to recognize this form of weak argumentation, look at this example of invalid reasoning:

    All Hong Kong people are brave.

    All brave people are highly-educated.

    Therefore, all highly-educated people live in Hong Kong!

    It is easy to see that the problem with the argument is in the fact that not all highly-educated people are referred to in the second premise.

    "All brave people are highly-educated" is not the same as "All highly-educated people are brave".

    The conclusion is an over-generalization: it is incorrect to refer to all highly-educated people.

    When confronted with this type of illogical reasoning, always ask if the conclusion necessarily follows from the premise.

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    Misuse of Statistics [ There are lies, damned lies - and statistics !  Anon.]

    Statistics are often used as evidence to support a claim.

    But, statistics can lie. You need to be aware of the potential misuse or abuse of statistics in argumentation.

    TASK: What is logically wrong with these statements? (or what information is conveniently missing?)

    1. There has been a 50% increase in our sales, compared with only a 25% increase for our competitors.
    2. Men in Hong Kong must be worse drivers than women, as 70% of drivers involved in accidents are men.
    3. An advertiser voted his product a big success because only 5 out of 100 buyers who had bought it had complained about its performance. "When 95% of buyers are pleased," the salesman was heard to say, "then that's a very good product."
    4. Hongkongers are better off than ever; their average worker’s monthly salary is now $20,000.
    5. Hong Kong people are fitter than ever. We are living longer. The average life expectancy at birth of males climbed from 67.1 years in 1970 to 71 years by 1983, and that of women from 74.7 years in 1970 to 78.3 years in 1983.

    Here are some comments on these 5 statements:

    1. Missing: absolute figures to see whether there has been a slight or a major catch-up effect; the competitors' sales might have started at 10 times what you were selling.
    2. Missing: what % of the total number of drivers are men?
    3. Extending not complaining to the dealer to meaning pleased. This is a clear example of the either-or assumption.
    4. A number of points:
    1. This example illustrates how a simplified argument can be simplistic. A number of other factors need to be taken into account. These figures are, for instance, likely to be influenced by

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    Summary TASK

    Detecting illogical reasoning and weak argumentation

    Read the following texts carefully. Note the viewpoint of each author and all the features you think should have been avoided:

    1. (Fictitious text)
    The idea that the people of Hong Kong should have the vote is a silly idea. They have no experience of democracy and the level of education is not high enough. It is well known that a high level of education is essential for the population to choose suitable candidates for office sensibly. The government knows what it is doing and is made up of experts in the field of decision making. To allow illiterate people the vote means that they will ruin the economy by making demands on public expenditure and forcing an increase in tax which is a bad thing. The economy of Hong Kong is a success story and to allow direct elections to the central legislature will destroy the base of stability and prosperity in the territory. Democracy may be alright for developed states but cannot be applied to Hong Kong because it is still a developing state. The model that we have for the future is much better for the territory.

    2. (Student text)
    I am strongly against decriminalising homosexual acts. Everyone realises that God has given us a distinctive sex identity. As we all know, it is natural that the normal majority are attracted to the opposite sex. This norm is widely accepted. Therefore homosexual behaviour should not be allowed under any circumstances

    Comments on Summary Task

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