A-level Critical Thinking

Credibility of evidenceEdit

  • Argument: A proposal/conclusion supported by a reason or reasons.
  • Evidence: Information that supports an argument.
  • Credibility: The believability of information.*

Source: Where information comes from e.g. a newspaper or a Website.

  • Truth – Something that is correct
  • Neutrality – A neutral source is impartial and does not take sides. The neutral source does not favour one point of view over another. Neutral sources are generally seen as more reliable.
  • Vested Interests – A person or organisation has a vested interest if they have something to gain from supporting a particular point of view. This can cause a person or organisation to lie, tell the truth, distort evidence or present one-sided evidence. Vested interests can increase or decrease the credibility of a source. Vested interests do not necessarily mean that a source will be biased.
  • Bias – Bias is a lack of impartiality. Biased sources favour a particular point of view. It has been argued that an unbiased source is impossible as everyone has a particular viewpoint

1. Propaganda 2. Bias can be seen in the selective use of language 3. Cultural bias – Ethnocentrism

  • Expertise – Expertise is specialist knowledge in a particular field. Experts are only regarded as knowledgeable in their own particular field.


·Experts disagree. ·Experts have made incorrect judgements . ·Some have argued expertise is harmful. (e.g. medicine) ·Expertise changes over time.

  • Reputation – Reputation is the regard in which a person or organisation is held. People can have good or bad reputations based upon their character, organisations can have reputations because of their actions. Newspapers can also have a reputation for quality and accuracy.
  • Observation- Eyewitness accounts are direct evidence. Evidence from those that saw an event firsthand .

Observations are affected by:

·Senses – short-sightedness would affect an eye-witness account. ·Memory – eye-witness accounts can be poor a long time after an event because memory can fade. ·Bias – Prejudice can distort an observation. ·Prior knowledge – Expertise can affect the way that an eye-witness account is told.

  • Corroboration – When more that one source of evidence supports the same conclusion. The evidence “points in the same direction”.
  • Selectivity – How representative information or evidence is. Surveys can be unrepresentative in terms of size and the type of people that they survey. To be neutral selected information should be representative of all of the information available.
  • Context – The setting in which information has been collected (e.g. a war-zone)

·The historic context – Attitudes can change over a period of time. ·The scientific context – The response to new scientific ideas if affected by what already known (e.g. Darwinism initially discredited). ·The journalistic context – Embedded reporters in a war zone – how accurate can they be? ·Interview context – People respond differently to different interviewers. ·Linguistic context – Language can affect the type of answers people give.

  • Credibility criteria: Criteria used to assess how believable a source of information is

1. Neutrality – How impartial a source of information is (biased or not). 2. Vested Interest – When a person or organisation have something to gain from supporting a point of view. 3. Expertise – Where the writer of information has specialist subject knowledge in a particular area. 4. Reputation – The regard in which a person of organisation is held in, based on their track record and their status. 5. Observation – A report from someone who directly perceived (heard, saw, felt) an event – an eyewitness account. 6. Circumstantial evidence - Physical evidence supporting the conclusion. 7. Corroboration – Where more than one source of evidence supports the same conclusion. 8. Selectivity – A measure of how representative information is compared with all of the information available. 9. Context – The situation in which information is collected.

An easy, quick way of remembering the main credibility criteria: C onsistency

  • R eputation
  • A bility to perceive
  • V ested interest
  • E xpertise
  • N eutrality / bias

Sources and types of evidenceEdit


  • Primary sources – sources from the time or period of study
  • Secondary sources – sources not from the time of study. These can include books with primary sources that have been processed and analysed by historians.


  • Primary evidence –new evidence collected as part of research
  • Secondary evidence – all other evidence such as government statistics.
  • First-hand evidence – eyewitness accounts from those who have directly observed an event.
  • Second hand-evidence – hearsay, evidence from those that have heard an account.
  • Direct evidence – eyewitness evidence .
  • Circumstantial evidence - non-direct evidence from which something can be inferred .
  • Statistics – can they be trusted?
  • Participant observation – does it affect behaviour?
  • Interviews – Does interview style affect the responses gained?
  • Questionnaires – Are they representative and will people be honest ?

Making a reasoned judgementEdit

  • Corroboration and conflict
  • Balance of evidence
  • Weight of evidence
  • Quality of evidence
  • Credibility criteria
  • Judgement

Unit IIEdit

  • Argument = Reason + Conclusion
  • Argument – The presentation of one or more reasons to support a conclusion.
  • Reason – A claim that supports a conclusion.
  • Conclusion – A claim that is supported by one or more reasons.
  • Argument indicator - A word which links a reason and a conclusion.

Arguments are often presented without using reason indicators. Reasons are different to evidence – evidence supports a reason.

The reasons and conclusions separated by an inference bar Conclusions can be identified by conclusion indicators (e.g. Therefore).

Some arguments have an intermediate conclusion – a conclusion before the main conclusion is stated.

Types of reasoningEdit

  • Simple reasoning – There is a conclusion that is supported by a reason.
  • side by side reasoning – Two reasons independent of each other support a conclusion.
  • Joint reasoning – Two reasons from which one conclusion can be drawn. It would not be possible to draw a conclusion from one of the reasons on its own.
  • Chain reasoning – Reasoning linked together.
  • Joint reasons: Reasons which have been used together to support a conclusion.
  • Assumption: An Assumption is an unstated reason
  • Principal: A principal is a general statement about how something should be. There are moral, legal and ethical principals. Principals are inflexible and cannot be bend to fit particular situations.
  • Counter argument: A counter argument is an argument that opposes another argument. Counter arguments can be included in an argument in order to dismiss that argument .
  • Counter claims: Counter claims or counter assertions are claims that are dismissed in an argument. The claims to not agree with the main conclusion.
  • A counter-example is an example that challenges the truth of a claim. Counter-examples challenge generalizations.

  • Hypothetical reasoning - Something will happen on the condition that something else happens .
  • Value judgements – A judgement based upon a value (e.g. murder is wrong). People have conflicting values and values change over time.
  • Definitions – Definitions are precise meanings of a word or phrase. Definitions can be argued other e.g. the definition of rape.

  • Causal explanations – Cause and effect (Smoking causes cancer).
  • A common cause – A correlation between two things is caused by a third factor.

A correlation between two things may be caused by chance .

  • Direction of causation – Does A cause B or does B cause A.

Some things have multi-causal explanations – explanations which show that there are more than one causes causing an effect.

An analogy is a comparison between two things which are seen to be similar .

Criteria to evaluate an argument by analogy 1.Number of instances 2. Number of similarities 3. Strength of conclusion 4.Relevance 5. Number of differences

Extreme analogies should be avoided as they can weaken an argument

Deductive and Inductive reasoningEdit

In a deductive the conclusion is deductively valid. If the conclusion is not guaranteed to follow from the reasons then the argument is invalid and the argument ceases to be a deductive reasoning.

Inductive arguments: Where is the reasons are true then the conclusion will probably be true. (Chelsea are 12pts ahead in the Premiership with only a few games to go it its likely that they will win the league).

In a strong argument reasons are only relevant if they make a difference to the conclusion.

Deductive reasoning: There the conclusion is guaranteed to follow from the reasons.

Inductive reasoning: If the reasons are true then it is likely that the conclusion is true.

Often there s a lot of evidence in arguments to support reasons which support conclusion.

Flaws in ArgumentsEdit

Appeal to Tradition

"we've always done it this way" Arguing that because something has always been done in one way in the past,it should continue to be done that way.

Appeal to Popularity

"Everyone likes them" Arguing that something must be the case or true or good because many people engage in an idea or activity.

Appeal to History

"If something has happened before, it will happen again." Arguing that what has happened in the past is always a guide to the future and/or the past will repeat itself.

Appeal to Emotion

"These poor puppies have been abandoned and you could give them the loving home they so desperately need." Arguing through tugging at peoples emotions rather than through logical reasoning/argument.

Appeal to Authority

Trying to persuade a reader to accept an argument based on the respect for authority rather than logic.

False Dichotomy

"either or" Reducing an argument to only two extreme options when there are other possibilities.

Restricting the Options

E.g" We blindfold him or we knock him out....or you just let your fiancee your wedding dress." Presents a limited picture of choices available in a situation in order to support one particular option.

Confusing Necessary and Sufficient Conditions

E.g "I have done everything necessary,registered and trained for the race. But is it sufficient/enough for me to win the race?" Necessary conditions are conditions which must be fulfilled in order for an event to happen. Sufficient conditions are conditions which, if fulfilled, guarantee that an event will happen. Some people confuse necessary and sufficient conditions.

Hasty Generalisation

Drawing a general conclusion from insufficient evidence/limited examples.


Putting two or more things together that aren't related. Treating two things as the same when in fact they aren't. eg. Obesity often conflated with lack of fitness.

Straw Man

Misrepresenting and exaggerating one part of the opponents argument in order to dismiss it and the entire argument. Changing or exaggerating an opponent's position or argument to make it easier to refute.

False Cause

Wrongly assumes a cause-and-effect relationship ('A' causes 'B' without proof that a relationship actually exists).

Slippery Slope

Making one or more unsupported leaps in an argument to arrive at an extreme conclusion.

Circular Argument

"People like dogs because dogs are kind pets which people like." Where a reason is the same as the conclusion, so the argument doesn't go anywhere as it just restates the argument rather than actually proving it.

Non Sequitur

Latin for "it does not follow." An inference or a conclusion that does not follow from the premises,evidence or reasoning given prior.

Ad Hominem

Latin meaning "against the man." In an argument, this is an attack on the person rather than on the opponent's ideas.

Post Hoc

Latin for "after this, therefore because of this." Arguing that because one thing follows another, the first caused the second. But sequence is not cause.

Add or remove terms from this set