Critical thinking & philosophy

Dilemma of the week

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The dilemma archive

Every dilemma we feature — open any one to think it through. This week's is highlighted and opened for you.

For any dilemma: write your honest first answer, then write the strongest case against yourself. Good thinking survives that test — and often changes because of it.

How to build a good argument

An argument isn't a row — it's a set of reasons (premises) that support a conclusion. Strong thinking means being able to take any argument apart and see whether it actually holds together.

Two tests matter, and they're different:

Validity — if the premises were true, would the conclusion have to follow?
Truth — are the premises actually true?

An argument can be valid but built on a false premise (so the conclusion is worthless), or have true premises that don't actually support the conclusion. A sound argument needs both.

Worked example. Premise 1: All swans I have seen are white. Premise 2: This bird is a swan. Conclusion: This bird is white. The logic feels tidy — but the first premise is false (black swans exist), so the conclusion isn't safe. Spotting which premise is doing the heavy lifting is half of critical thinking.

Three habits of strong reasoners:

Find the hidden assumption. Most weak arguments rely on something unstated. Drag it into the light.
Steelman, don't strawman. Before you disagree, state the other side's case so well that they'd say "yes, exactly". Then respond to that.
Separate evidence from assertion. "Everyone knows…" and "it's obvious that…" are not evidence.

Spot the fallacy

Weak arguments hide behind these moves. Learn to name them, then hunt for one in a newspaper, advert or social-media post this week.

Ad hominem

Attacking the person, not the argument.

"You can't trust her economics — she's never had a real job."

Straw man

Swapping the real claim for a weaker one.

"He wants cycle lanes, so he must want to ban cars."

False dilemma

Pretending there are only two options.

"Either we cut the budget or the service collapses."

Slippery slope

Claiming one step must lead to an extreme.

"Allow this and where will it end?"

Appeal to authority

True just because someone famous said it.

"A celebrity endorses it, so it works."

Correlation ≠ cause

Two things rise together, so one caused the other.

"Ice-cream sales and drownings both peak in summer."

Circular reasoning

The conclusion is hidden inside the premise.

"It's the best because nothing is better."

Hasty generalisation

A sweeping rule from too few cases.

"Two rude tourists — that whole country is rude."

Appeal to emotion

Stirring feelings in place of reasons.

"Think of the children!" — but is the claim true?

Mind the bias

Fallacies are faults in arguments; biases are faults in thinking — the shortcuts your own brain takes without telling you. Knowing them helps you catch yourself.

Confirmation bias — noticing evidence that fits what you already believe, ignoring the rest.
Anchoring — the first number you hear drags your estimate towards it.
Availability — judging how likely something is by how easily examples spring to mind (so rare-but-vivid events feel common).
Sunk cost — carrying on with something because of what you've already spent, not what's still worth it.
Dunning–Kruger — the less you know about a topic, the more confident you can feel.

Reasoning challenges

Try each before you open the answer.

"This sentence is false." Is it true or false?
Reveal
If it's true, then it's false; if it's false, then it's true. It's a paradox — a self-referential sentence that can't take a stable truth value. Mathematicians and logicians (Russell, Gödel) built whole theories wrestling with exactly this.
Two guards stand at two doors — one always lies, one always tells the truth — but you don't know which is which. You may ask one guard one question to find the safe door. What do you ask?
Reveal
Ask either guard: "Which door would the other guard say is safe?" — then choose the opposite. Both a lie about a truth and a truth about a lie point you wrong, so reversing it points you right.
Can something be "true for you" but false for someone else? Find an example that genuinely works — and one that only seems to.
Reveal
"Liquorice is delicious" can be true-for-you (it's about preference). "The Earth is flat" cannot — it's a claim about the world, not about you. Many disagreements dissolve once you spot which kind you're having.
If a test for a rare disease is "99% accurate" and you test positive, are you 99% likely to have it?
Reveal
No — and this surprises almost everyone. If the disease is very rare, most positive results are false positives, because there are far more healthy people to misclassify. This is base-rate neglect; look up Bayes' theorem.

Where next

Oxplore — Oxford's "home of big questions" for curious teenagers.
Philosophy Bites — short interviews with leading philosophers.
BBC In Our Time — deep discussions on ideas across history, science and philosophy.
TED-Ed — short, sharp videos, many on logic, paradoxes and how to argue well.

Produce & share

Make something: Choose one dilemma and write a one-page response that argues your view — but first states the opposing case so fairly that its supporters would agree you've understood them. Then explain why you still disagree (or why you changed your mind).

When it's ready, email your work to Mr King. The best pieces may be featured in the student showcase.

What you'll practise

Analysing arguments, separating reasons from rhetoric, recognising your own biases, holding two views at once, and changing your mind for good reasons — the foundations of every strong essay, interview and debate.