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NotesPhilosophy HLTopic 10.12Liberty of thought and discussion
Back to Philosophy HL Topics
10.12.22 min read

Liberty of thought and discussion (Philosophy HL)

IB Philosophy • Unit 10

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Contents

  • Silence one voice — even a wrong one?
  • Three reasons never to silence an opinion
  • Dead dogma vs living truth
The big idea: Picture an opinion almost everyone thinks is false — even offensive. Should we be free to silence it?

Mill's startling answer is no, and his reasons aren't about being polite. He argues that silencing even a false opinion robs everyone else, not just the speaker.
Mill's claim: "If all mankind minus one were of one opinion… mankind would be no more justified in silencing that one person than he, if he had the power, would be justified in silencing mankind."

His point: to silence an opinion is to assume you can't possibly be wrong — and history is full of confident majorities who were. He calls this the assumption of infallibility.

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Mill gives a tidy three-part case, and it's worth learning as three.

Mill's three reasons

1

1. The silenced view might be TRUE

If we ban it, we assume we can't be wrong. But majorities have been wrong before — so we might be burying the truth.

2

2. It might be PARTLY true

Most opinions hold a piece of the truth. Clashing views let us collect the missing pieces from each side.

3

3. Even if it's false, we need it

A true belief never challenged becomes 'dead dogma' — held by habit, not understood. Opposition keeps it a living truth.

Wrong · Part-true · Dead dogma

Checkpoint — the three reasons: In one line: silence an opinion and you might bury the truth, lose a half-truth, or let your own truth rot into dead dogma. Hold the three — the next idea is what a live truth actually feels like.

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Mill's third reason is the one students most often miss, so it's worth its own moment.

The truth you can't defend: Think of a belief you hold but have never really been challenged on. Could you argue for it against a clever opponent? Mill says that if you can't, you don't fully own it — you're repeating a dead dogma. It's only by meeting real opposition that a belief becomes a living truth — one you understand and can defend.
Go further — higher-level insight: Spot what Mill is NOT saying. He isn't saying 'all opinions are equally valid' or 'truth doesn't exist'. The opposite — he cares about free speech because he thinks there's a truth worth reaching, and open debate is how fallible people get closer to it. Naming that (free speech in the service of truth, not relativism) is a top-band point.
Checkpoint — dead dogma: In one line: a truth never challenged is held blindly; opposition is what turns dead dogma into a living truth you actually understand.

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what Mill means by the 'assumption of infallibility'. [2 marks]

Related Philosophy HL Topics

Continue learning with these related topics from the same unit:

10.1.1The verification principle
10.1.2Eliminating metaphysics
10.1.3Emotivism
10.1.4Does verificationism defeat itself?
View all Philosophy HL topics

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