What Does It Take to Know Something?

"What is knowledge?" is one of the oldest questions in philosophy, and it remains unsettled. This page is a reading path of six texts, each with a writing prompt, so that you form your own view instead of memorising someone else's. The status of the page is Aporetic: the texts are well established, but the central question has no agreed answer.

Why the question comes first

Every other method in this wing assumes some answer to it. If you cannot say what would count as knowing, you cannot say whether a test, a proof or a study has delivered it. A common starting definition is that knowledge is justified true belief, an idea that Plato's Theaetetus tests without endorsing. The path below shows both the appeal and the trouble with that definition.

The reading path

The first stop has its own guide at Peirce on the Fixation of Belief. Read it before the other five.

Peirce, "The Fixation of Belief"

Peirce compares four ways of settling belief and argues that only the method of science answers to something outside our opinions. Writing prompt: name a belief you hold firmly and say which of the four methods produced it.

Peirce, "How to Make Our Ideas Clear"

Peirce proposes the pragmatic maxim: to understand a concept, consider the practical effects it might conceivably have. Writing prompt: apply the maxim to a technical term you use daily, such as "secure" or "available". What observable differences would the term make? If you cannot name any, what does that say about the term?

Clifford, "The Ethics of Belief"

Clifford argues, with a shipowner example, that "it is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence." Writing prompt: is Clifford's rule self-refuting? Ask whether the rule itself is supported by sufficient evidence, and what kind of evidence could support a moral rule of this sort.

James, "The Will to Believe"

James replies that when a choice is live, forced and momentous, and cannot be settled on evidence alone, we may let our passional nature decide. Writing prompt: test Clifford and James on one real decision you faced. Who wins, and under what conditions? Compare this with how decisions are made in Judgment Under Uncertainty: Probability, Causation and Forecasting.

Plato, Meno

In the Meno, Socrates leads an untrained slave boy to double the area of a square (82b-85b). The boy first proposes doubling the side, then discovers that the diagonal gives the answer. Writing prompt: work the geometry yourself with a pencil. Did Socrates teach the boy anything, or only ask questions? Compare with the elenchus and Plato's Divided Line on the academy page.

Gettier

In 1963 Gettier gave short cases in which a person has a justified true belief that seems not to be knowledge because the truth is a matter of luck. Writing prompt: build a Gettier case from everyday troubleshooting. For example, a technician believes "this cable is faulty" because a tester shows errors. The tester's label was swapped, so the reading actually came from a different cable. By coincidence the cable in question is also faulty. The belief is justified and true, but is it knowledge? See Stale Information and Dependable Reports for related cases where a report is believable but out of date.

Companion texts

Plato's Theaetetus (201c-210d) considers whether knowledge is true belief plus an account, and ends without a resolution. Aristotle's Posterior Analytics I.1-2 describes demonstrative knowledge as knowing the cause and why the thing cannot be otherwise. Both belong to the history that The Seven Liberal Arts, Hands-On: Logic, Proof and the Quadrivium covers in practice.

Milestone essay

After the path, write 1,500 to 3,000 words with this structure:

1. Question. State exactly what you are asking.
2. Thesis. Your answer in one or two sentences.
3. Objection. The strongest case against you.
4. Reply. Why you still hold your thesis, or what you changed.

A good thesis may be modest, for example "knowledge requires justification that tracks the truth, and no single feature suffices." Keep the claims you cannot defend out of the thesis. The care you take here connects to Reasoning for What Ends? Wisdom, Character and the Examined Life, since what we are entitled to believe matters partly because of what we then do. For evidence-based beliefs in daily life, see Reading Nutrition Evidence: What a Study Can and Cannot Show.

What remains open

Philosophers have proposed many responses to Gettier, including requiring that justification not depend on a false belief, reliabilist accounts, and virtue epistemology. None has gained general agreement. Treat the question as Aporetic: you can make progress on it without expecting a final answer.

Try this

1. Do the Meno geometry on paper and note exactly where the boy's first answer fails.
2. Write a Gettier-style case from a field you know well in two paragraphs, then say whether you would call it knowledge.
3. Draft the milestone essay's question and thesis, and share the thesis with someone who will object.

Further reading

• Plato, Meno and Theaetetus (many translations; Grube's Meno is widely used).
• Edmund Gettier, "Is Justified True Belief Knowledge?", Analysis 23(6) (1963), pp. 121-123.
• Stephen Hetherington (ed.), Epistemology: The Key Thinkers (Continuum, 2012).
• Stanford Encyclopedia of Philosophy, entries "The Analysis of Knowledge" and "Epistemology".