Great IdeasKnowing and thinking
Truth
What it means for something to be true, and how we can tell.
The question
What does it mean for something to be true? And how do we find the truth when people disagree?
How the books answer
Oldest first. Each stop is our own short summary of what the author argued; follow the link to the rung for the whole lesson.
c. 375 BC
Plato, The Republic, Books VI–X
For Plato, the truest things are the unchanging Forms, and the highest of them, the Good, is like the sun that lets us see everything else. Finding truth means turning the whole soul toward it. Opinions about changing things are only half true.
c. 350–322 BC
Aristotle, Metaphysics
Aristotle gives a plain account: to say of what is that it is, and of what is not that it is not, is true. He also defends the rule that a thing cannot both be and not be in the same respect at the same time. Without that rule, he says, no one could argue about anything.
“It is, that the same attribute cannot at the same time belong and not belong to the same subject and in the same respect…”
AD 396–426
Augustine of Hippo, On Christian Doctrine
Augustine tells Christian readers not to fear the learning of pagan writers. Whatever is true, he says, comes from God, wherever it is found. He compares useful learning to treasure carried out of Egypt.
“Let every good and true Christian understand that wherever truth may be found, it belongs to his Master.”
1644–1671
John Milton, Areopagitica, the English minor poems, Samson Agonistes
Milton argues that truth is strong enough to win in open argument. Licensing books before printing, he says, treats readers like children and keeps truth from growing. Truth needs to meet falsehood face to face.
1859
John Stuart Mill, On Liberty
Mill adds that even when we are right, we need to hear the other side. A truth that is never challenged becomes a dead slogan instead of a living belief. And the silenced opinion might hold part of the truth we lack.
1879–1892
Henrik Ibsen, The Wild Duck
In The Wild Duck, a young man is determined to reveal a family's hidden past, sure that truth will set them free. Instead it brings disaster. A cynical doctor says ordinary people need their comforting illusions, and Ibsen leaves the audience to weigh both sides.
“Rob the average man of his life-illusion, and you rob him of his happiness at the same time.”
1886
Friedrich Nietzsche, Beyond Good and Evil
Nietzsche asks why we want truth at all, and whether philosophers' systems are really personal confessions. He suspects that much of what passes for truth serves the needs of those who hold it. Readers still argue over whether he meant to reject truth or to demand a harder honesty about it.
“It has gradually become clear to me what every great philosophy up till now has consisted of—namely, the confession of its originator, and a species of involuntary and unconscious auto-biography.”
1907
William James, Pragmatism
William James suggests a practical test: what difference would it make if an idea were true? True ideas, he says, are the ones we can check and that guide us well through experience. His critics answered that something can be useful and still be false.
“True ideas are those that we can assimilate, validate, corroborate and verify.”
1912
Bertrand Russell, The Problems of Philosophy
Russell answers James. A belief is true, he argues, when it matches the facts, and false when it doesn't, whatever it does for us. Truth depends on the world, not on what we would like.
For young readers
Something is true when it matches how things really are. If you say 'it's raining' and it is raining, that's true. If it's sunny, it isn't.
Finding the truth can be hard when people disagree. One good way is to listen to both sides, look at the evidence and be willing to change your mind. Milton thought truth wins if it gets a fair fight.
Talk about it
- How can you tell if something you hear is true?
- Mill says we should listen to people we disagree with. Why might that help us?
- Is it ever kind not to tell the truth? What does The Wild Duck suggest?
- James asks what difference a truth makes. Can something be true but make no difference?
- What is a time you changed your mind because of new facts?
Where else on the site
- Judging Sources
- Kinds of Evidence
- Evaluating an Argument Step by Step
- Counterarguments
- Real and Fake
- Honest and Dishonest
Every rung tagged with this idea:
These pages are our own short synthesis, written for families. They were inspired by Mortimer J. Adler's Syntopicon, the index of great ideas in volumes 1 and 2 of Great Books of the Western World, but the questions, summaries and groupings are ours, not the Syntopicon's. Short excerpts come from public-domain translations, credited where they appear.