Validity vs. Soundness
Two arguments can have the exact same logical structure yet one can be strong and the other absurd — the difference lies in validity versus soundness. You will be able to test any argument for both.
Validity: Does the Structure Work?
An argument is valid if the conclusion would have to be true whenever the premises are true, regardless of whether the premises are actually true. 'All fish can fly. Sharks are fish. Therefore, sharks can fly' is perfectly valid — the logical structure is airtight — even though it is obviously false in reality.
Soundness: Are the Premises Actually True?
An argument is sound only if it is valid AND its premises are actually true. This is the real test a BQ judge should apply: a valid argument built on a false premise still proves nothing, so attacking a premise's truth is often more powerful than attacking logical structure.
Attacking the Premise Judges Will Actually Notice
When time-pressed in rebuttal, choose to attack whichever premise the judge is most likely to find intuitively doubtful, not necessarily the philosophically weakest one — persuasion in front of a lay judge often outperforms pure logical precision.
Negative argument: 'Only physical things exist. Free will, if real, would be non-physical. Therefore, free will does not exist.'
This argument is valid — if both premises are true, the conclusion follows necessarily. The Affirmative's best strategic move is not to attack the logical structure (which is fine) but to attack the truth of premise one, arguing that mental states may be physical processes in the brain, making the argument valid but unsound.
1. An argument with true premises and a logically necessary conclusion is:
2. An argument can be valid but still prove nothing useful if:
3. True or False?
"If an argument is valid, its conclusion must be true."
Answer all 3 to check.
Judge every argument in two steps: is it valid (structure), and is it sound (true premises) — most real clash happens over soundness.