What is knowledge?

The big idea: You say 'I know it's raining' and 'I know my friend's name' without a second thought.

But push on it: what's the difference between really knowing something and just believing it, or getting lucky with a guess? Epistemology — the study of knowledge — starts by trying to pin that down.

There's a famous three-part answer. To know that something is the case, philosophers say three things must line up at once.

The traditional definition, traced back to Plato, breaks knowledge into three ingredients that must all be present.

Checkpoint — JTB: In one line: you KNOW something when you believe it, it's true, and you have a good reason for it — all three at once. Miss any one and it isn't knowledge.

Go further — higher-level insight: The philosopher Edmund Gettier famously built odd cases where all three boxes are ticked — true, believed, justified — yet it still feels like luck, not knowledge. You don't need the details, but knowing JTB has been challenged shows the definition isn't the last word. It's a great point to nod to for a top-band answer.

'Know' actually covers three quite different things — and the JTB recipe only really fits the first.

A third kind: knowing by acquaintance: There's also knowledge by acquaintance — 'I know Paris' or 'I know my best friend'. This isn't a fact you memorised or a skill you practise; it's knowing something because you've met it directly. You could know every fact about Paris from a book and still not know Paris the way someone who has walked its streets does.

Checkpoint — three knowings: In one line: knowing-that is facts, knowing-how is skills, and knowing-by-acquaintance is direct contact. When people argue about 'knowledge', they usually mean the first.