Critical Thinking A-Level Revision Notes

Critical thinking revision

What is an argument?

- An attempt to persuade someone of a point of view by using reasoning. It is made up of three parts:

  • Reason – a cause that makes something happen & answers the question ‘why…?’
  • Conclusion – a result or judgement that has been caused by the reason. It doesn’t always mean the final point in a written passage.
  • An element of persuasion – something that tries to influence you into believing or doing something.

DON’T BE MISLEAD – other forms of language can sometimes be included to confuse you:

  • Opinion – a statement of what someone thinks or believes. It is not based on fact that can be tested.
  • Assertion – an attempt to persuade but doesn’t include reasons. It is an opinion with an element of persuasion, e.g. ‘you should do this.’
  • Explanation – a statement that includes at least one reason and a conclusion but doesn’t include an element of persuasion, e.g. ‘my critical thinking class has both sexes in it because my teacher wants us to have discussions from both perspectives.’

Identifying conclusions

  • Indicator words and phrases – help the reader to identify a particular part of an argument.
  • Conclusion indicator words – act like a signal to tell us which phrase or sentence is the conclusion of the argument. E.g. therefore, so, as a result, consequently, which proves that, this means that, it follows that, thus, hence, etc.
  • Sometimes indicator words are not present so you need to:

-Find the phrase or sentence that you think represents the overall point of view the writer wants you to accept.

-Try putting an indicator word like ‘therefore’ or ‘so’ immediately before this phrase or sentence to see if it makes sense.

Identifying reasons

  • A reason is a rational statement that aims to persuade the reader to accept a conclusion
  • Reason indicator words include:

-For the reason that, seeing that, as, because, in view of the fact that, seeing as, since, given that, etc.

  • Indicator words that link reasons include:

-In addition, also, as well as, etc.

Counter assertions and counter arguments

  • Counter assertion - a statement (or claim) that goes against the main conclusion of the argument
  • Counter argument – a complete mini-argument that opposes the main conclusion of the argument – it includes all three elements of an argument.
  • The main difference between counter assertions is that counter arguments include a reason / some reasons
  • Counter arguments and counter assertions are included so that they can be made to look weak. This, in turn, strengthens the whole argument.


  • Evidence – used to develop, strengthen or support a reason in an argument. It is usually in the form of numbers and the data can be from research, surveys, statistical calculations, etc.

NOTE: the numerical reference can be qualitative, e.g. ‘in a survey most people preferred to shop at Tesco’ – this is still evidence even though…

Chapter 3 - Truth versus logical strength    Premises and conclusions may be truth or they may be false Evaluating the truth - value of premises and conclusions is distinct from evaluating the logical strength of arguments Eample: 1. Ryerson University is in Guelph,On 2. The RAC is locsted within Ryerson U 3. Therefore, the RAC is located within Ryerson U    This is a deductive and valid argument, all the premises could be false The logical strength is really good What is deductive validity   An argument is deductively valid if and only if it is not possible for the premises to be true and the conclusion false I.e if all the premises Were true, the conclusion would also have to be true too an argument is deductively invalid if and only if it is not deductively valid. A deductively valid argument is truth preserving, if you put true premises in you get a true conclusion A deductively valid argument 1. All bachelors are unmarried 2. Ivan is a bachelor 3. Therefore, ivan is unmarried   Its valid bc the premises would guarantee the truth of the conclusion Is this valid or invalid explain An invalid argument 1. Some politicians smoke marijuana 2. James is a politician 3. Therefore, Jones smokes marijuana  This is invalid bc of the use of the word some and the premises dont gurantee the conclusion If anargument is calid must the premises be true. Explain. No, valid doesnt mean that the premises is true... In order to be valid an argumemt does not have to hace true premises and it doesnt have to have true conclusions: whats important is the logical Relationship betweem the premises and conclusion Deductive soundness True or false a sound argument with true premises could it have a false conclusions false, An argument is deductively sound if and only if it is deductively valid andall its premises are true if its sound that means it valid if its valid it means the conclusion , must true 1. 2. 3. 4. Some politicians are male Some males are bachelors Therefore, some politicians are bachelors Its invalid because its not enough info Valid with false premises and a true conclusion 1. All politicians are make 2. Alll males are bachelors 3. Therefore, some politicians are bachelors



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