Inductive, Deductive & Abductive Reasoning – Key Points

Critical Thinking & Good Arguments

• Goal: hold beliefs only when backed by good reasons (raise likelihood of truth).
• A persuasive argument satisfies three conditions:
  • Acceptability – premises likely true.
  • Relevance – premises directly support claim.
  • Grounds – premises jointly sufficient for conclusion.

Deductive Reasoning (Review)

• Moves from general rule to specific case.
• If form is valid and premises true, conclusion cannot be false (soundness).
• Powerful yet applies only where premises fully determine outcome.

Inductive Reasoning

• Starts with specific instances → infers generalisation or prediction.
• Truth of conclusion probable, not guaranteed by premises.
• Common in science for learning new information.

Evaluating Inductive Arguments

• Graded as Strong or Weak (quality of inference), not valid/invalid.
• Classified as Cogent (true premises + strong) or Uncogent (otherwise).
• Strength of claim ≠ strength of argument; moderate conclusions often stronger.

Types of Inductive Arguments

• Generalisations – extract common property \to broad rule.
• Analogies – shared features in A & B \to expect further shared feature.
• Causal Inference – repeated temporal correlation \to propose cause–effect link.

Abductive Reasoning

• Forms the most likely & simplest explanation for observed facts ➜ "inference to best explanation".
• Similar to induction; premises do not entail conclusion.
• Quality judged by plausibility, simplicity (Occam’s Razor), and consistency with evidence.

Qualities of a Strong Overall Argument (Any Type)

• Claim clearly stated.
• Adequate, directly supportive evidence.
• Addresses counter-arguments/counter-evidence.
• Logical, transparent structure leading reader to conclusion.
• Appropriate, precise language.

Looking Ahead

• Next focus: logical fallacies & cognitive biases – common traps that undermine reasoning.
• Remember Feynman’s warning: we are "the easiest person to fool" – stay vigilant.