Critical Reasoning: Assumptions, Flaws, and Argument Techniques

Necessary Assumptions

Statements that must be true for the argument to hold.

Common phrasing for Necessary Assumptions

'Which of the following is an assumption required by the argument?' and 'The argument presupposes which of the following?'.

Example of Necessary Assumption

If an argument claims that 'All birds can fly', a necessary assumption might be 'The subject in question is a bird'.

Negation Test

If negating the assumption makes the argument invalid, it is necessary.

Importance of Necessary Assumptions

They often go unstated, making them critical for understanding the argument's structure.

Sufficient Assumptions

Statements that, if true, guarantee the conclusion of the argument.

Common phrasing for Sufficient Assumptions

'Which of the following, if assumed, allows the conclusion to be properly drawn?' and 'Which assumption makes the argument valid?'.

Example of Sufficient Assumption

In an argument stating 'If it rains, the ground will be wet', a sufficient assumption could be 'It is raining'.

Identifying Sufficient Assumptions

Determining which statement, if added, would make the conclusion logically follow.

Strengthening Arguments

Strengthening questions ask for information that makes the argument more likely to be true.

Common phrasing for Strengthening Arguments

'Which of the following most strengthens the argument?' and 'Which provides the strongest support?'.

Example of Strengthening Statement

If an argument claims 'Exercise improves health', a strengthening statement could be 'Studies show regular exercise reduces heart disease risk'.

Weakening Arguments

Weakening questions focus on information that undermines the argument's validity.

Common phrasing for Weakening Arguments

'Which of the following most weakens the argument?' and 'Which casts doubt on the argument?'.

Example of Weakening Statement

If an argument states 'All swans are white', a weakening statement could be 'There are black swans in Australia'.

Flaw Questions

Require identifying logical mistakes in the argument's reasoning.

Common phrasing for Flaw Questions

'The argument is flawed because...' and 'Which of the following most accurately describes a flaw?'.

Example of a Flaw

Assuming that correlation implies causation, such as 'Since ice cream sales increase in summer, ice cream causes warm weather'.

Inference Questions

Ask for statements that logically follow from the argument.

Common phrasing for Inference Questions

'Which of the following must be true?' and 'Which can be logically inferred?'.

Example of Inference

If the argument states 'All mammals are warm-blooded', an inference could be 'Whales are warm-blooded'.

Method of Reasoning Questions

Focus on how the argument is structured and the techniques used.

Common phrasing for Method of Reasoning Questions

'The argument proceeds by...' and 'Which describes the argumentative technique?'.

Parallel Reasoning Questions

Require finding arguments with similar logical structures.

Common phrasing for Parallel Reasoning Questions

'Which argument is most similar in reasoning?' and 'Which exhibits the same pattern?'.

Principle Questions

Ask for rules that justify or support the reasoning in the argument.

Common phrasing for Principle Questions

'Which principle justifies the reasoning?' and 'Which principle supports the argument?'.