Knowing whether an argument is valid is one of the most important analytical skills in the Extended Investigation. Validity is a technical term — it does not simply mean “correct” or “convincing.” Understanding its precise meaning allows you to assess the logical quality of any argument you encounter.
| Term | Definition | Requires true premises? |
|---|---|---|
| Valid | The conclusion must follow from the premises — if the premises were true, the conclusion could not be false | No |
| Sound | Valid AND all premises are actually true | Yes |
An argument can be valid but unsound if it has correct logical structure but one or more false premises. In research, you must check both the logic and the truth of the premises.
Example of valid but unsound:
1. All VCE students hate exams. (premise — false)
2. Jesse is a VCE student. (premise — true)
3. Therefore, Jesse hates exams. (conclusion — logically follows, but the argument is unsound)
KEY TAKEAWAY: Validity is about the form of the argument (does the conclusion follow?). Soundness is about the content (are the premises true?). A good argument must be both. Examiners expect you to distinguish between these when critiquing research.
A valid argument has these features:
In a deductively valid argument, if all premises are true, the conclusion cannot be false. The standard form is the syllogism:
This form is used in Extended Investigation when making logical inferences from theoretical frameworks.
Most research arguments are inductive, not deductive. Inductive arguments cannot guarantee their conclusions — they aim for probability and strength instead.
A strong inductive argument has:
- A large, representative sample
- Multiple converging lines of evidence
- Conclusions that are appropriately qualified (“suggests,” “is likely,” “provides evidence that”)
- Acknowledgement of alternative explanations
EXAM TIP: When asked to evaluate whether an argument is “valid,” check: (1) Does the conclusion follow from the premises? (2) Are there any logical gaps or fallacies? (3) Are the premises themselves well-supported? Address all three for full marks.
Watch for these warning signs:
- Missing premises: The conclusion requires an assumption that is never stated
- Non sequitur: The conclusion does not follow from the premises (“This does not follow”)
- Circular reasoning: The conclusion is hidden within a premise
- Overgeneralisation: Drawing sweeping conclusions from limited evidence
- False dichotomy: Presenting only two options when more exist
When reviewing sources for your Extended Investigation, ask:
- What is the main conclusion?
- What premises/evidence support it?
- Does the conclusion follow from those premises?
- Are any steps in the reasoning missing or unjustified?
Document your assessments in your Extended Investigation Journal — assessors can see your critical thinking process.
REMEMBER: In your own written report, aim for inductive strength rather than deductive certainty. Use hedging language (“the evidence suggests,” “this finding is consistent with”) rather than overclaiming. Overclaiming is itself a form of invalid reasoning.
