Critical thinking and how to do it!

A Identifying arguments – these are attempts to persuade to a point of view – not arm twisting, not explaining!

a) Using reasons
b) Always have a conclusion i.e. a p.o.v not necessarily at the end.
c) The conclusion is based on the reasons which accompany it:

Words as clues:

Therefore so then thus should must

Do the reasons support the conclusions?

Are they relevant?

Are they adequate? If it seems to prove something – yes. But can depend on how strong the conclusion is i.e. will / probably / might – getting weaker!

B Analysing simple arguments – sometimes the reasons are not sufficient to lead to the conclusion.

Showing argument structure as a diagram:

R= reason C= conclusion

If the reasons are linked i.e. if they cannot be removed from each other without weakening them add + e.g.

    R1 smoking’s not illegal
    R2 millions get pleasure from it

    C Therefore people should be allowed to smoke anywhere

    R1 overcrowding in prisons is a cause of many riots
    R2 most of our prisons are overcrowded
    C Therefore riots are likely in the coming months

Cutting out the crap!

Some arguments include additional material, padding etc so find the conclusion first, then work out if the reasons support only the conclusion, nothing else [Think Aquinas’…and this we call God]

Certainty or probability?

  • Deductive arguments are those in which the conclusion is drawn with certainty [think of the ontological argument]
  • Inductive are those which are only probable.

If the premises are true then the conclusion must be too. So long as you agree with the reasoning it is illogical to disagree with the conclusion.

Sometimes, though, you can draw a different conclusion from the reasons given (e.g. global warming and the melting of the ice-caps.)

C Finding more detail in arguments

Finding more than one conclusion:

(R1) icecaps melting —> (R2) must be global warming —> (C) so sea levels will rise —> thus leading to flooding

Therefore the first conclusion is used as a reason for the second conclusion. The first becomes an intermediate conclusion leading to the main conclusion.
R —> 1C —> C

Of course sometimes a further reason can follow the I.C.

Can you show that the I.C. may be unsound? Or that its use as a reason is dubious? If so you have evaluated the effectiveness of it as an argument.


Sometimes there are hidden assumptions taken for granted e.g.

Most of the children at the school performed less well than those at other schools, therefore the quality of the teaching must be poor.

The assumptions here are many! Are there no other differences? E.g. Intake? Disruption? Ability? Socio-economic background? Etc yet here we are given only one reason and one conclusion.

So remove the assumptions and the argument is weakened.

Using analogies [think religious language]

This means using one situation to draw a conclusion about another similar. The similarity is assumed and the conclusion drawn without the similarity being argued. Is it even a good reason?

Look for similarities and differences between the two situations – if the similarities are much stronger than the differences then the analogy is good, if not it weakens the argument.

Of course it can never put the conclusion beyond doubt.

Check for relevance and adequacy – is the supposedly similar situation real or imaginary? If imaginary it’s weaker than a real example. So does it highlight an issue? If yes then this is its strength. The example in the book is of alcopops needing greater regulation just like chocolate flavoured cigarettes would too. [Think the lottery example in the ontological argument – how much greater it is to win in reality than in imagination!]

D Exploring weakness

Necessary and sufficient conditions

Something may be a necessary condition of x but is it sufficient?

Even if x and y are found together there isn’t necessarily a relationship.

[think David Hume and cause and effect and also natural laws.]

Beards and great thinkers is the example in the book!

If x = being fairly fit and y= running the marathon distance it can be seen that x is necessary but isn’t necessarily sufficient!

So necessary and sufficient where x is present y must occur, e.g. the heir ton the throne is the eldest son of the reigning monarch – both necessary and sufficient to be the oldest son, neither qualifications nor age no marital status make a difference.

Confusing causes and consequences

Assuming x is the cause of y when it may be mere coincidence. [think miracles]

Nevertheless causal arguments can be strong but only if it explains what the link is between cause and consequence.

Asking questions about the evidence

  1. is the evidence sufficient to draw the conclusion?
  2. Are there other explanations as plausible as the one the author concludes? [miracles]
  3. Is there a relationship between the evidence such that if one piece is accepted another must be rejected?
  4. What assumptions is the author making? [Religious experience]
  5. How could the argument be made stronger?

Attacking the arguer rather than the argument

In this kind of argument it is the people who make the claim rather than the claim itself which is attacked “people like them…” and this is rarely a valid kind of argument. (Tabloid newspapers often do this and use irrelevant reasoning.)

Going round in circles

Sometimes the conclusion is no more than the reason reworded!

A leap too far [Hume of the teleological argument]

Building strawmen

Reworking the opposition’s argument to highlight its weakness then attacking that instead of the original version, thus attacking your opponent’s conclusion rather than their reasons!

Two wrongs don’t make a right

“Not fair” / “other people do it” i.e. a counter accusation – offence being the best form of defence! (typical in the classroom: “I wasn’t the only one talking!”)

“You too” or “so do you” arguments

Like the above except where there may be relevance – countries cutting down their rainforests and being accused of damage to the environment turning the criticism back on the industrialised nations i.e. there is some justification for this kind of argument.

Restricting options

Watch out for writers who only allow an either / or scenario with no other options e.g. “we must either poison or shoot the pigeons or allow the city to become a dirty disease ridden place.”

Making irrelevant appeals

Appealing to popularity – “most people say / do / think… therefore it must be true.”!

Appealing to pity – “it’s not fair.” – is that relevant? What were the criteria?

E Finding strengths – deductive arguments

Do the alternatives exhaust the possibilities? If so then the conclusion must follow and be certain if not then the conclusion may fail and be only probable.

Building a chain of argument

If A is true then B is true then C must be true [ontological argument: If God is the greatest being imaginable then he must exist for not to exist would mean he is not the greatest being imaginable.]

Thus if the ifs are true then the thens must be!

F Assessing the credibility of the evidence

Look for motive

Check for corroboration

Look for vested interest

G And finally applying your skills

Asking the right questions:

  • What conclusion does the author come to?
  • What reasoning does the author use to support this conclusion?
  • What assumptions are necessary for this conclusion to be drawn?


  • Does the reasoning support the conclusion?
  • Does the evidence have the significance the author intends?
  • Are there other explanations for the evidence?
  • If the author uses any analogies do they work?

Use these to assess an argument – E.g. Try the exercises on pages 101-113

Remember you can use the same skills to strengthen arguments that you write, just remember to:

  • Check that your evidence supports the conclusion you want to make
  • Do you need more evidence?

Good luck!


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