What Is Knowledge?

Knowledge as Justified True Belief

Since Plato, philosophers have defined knowledge as justified true belief (JTB). To know something, three conditions must be met: you must believe it, it must be true, and your belief must be justified — that is, you must have good reasons for holding it.

Belief alone is not enough: you might believe the earth is flat, but that is not knowledge because it is not true. True belief alone is not enough: you might believe correctly that a coin will land heads, but if you had no reason to believe it, that is luck, not knowledge. Justification is what transforms true belief into knowledge.

This framework matters for media literacy. When you read a news claim, you are evaluating justification: what evidence supports this claim? Is the evidence sufficient? Could the conclusion be true by coincidence rather than because the evidence establishes it?

The Gettier Problem: Knowledge Is Harder Than You Think

In 1963, philosopher Edmund Gettier published a three-page paper that upended 2,400 years of epistemology. He showed that you can have a justified true belief that is not knowledge. Consider: you see what appears to be a sheep in a field. You form the justified belief 'There is a sheep in the field.' In fact, what you saw was a dog dressed in a sheep costume — but behind the hill, hidden from your view, there is a real sheep. Your belief is justified (you had visual evidence), it is true (there is a sheep), but it is not knowledge because your justification does not connect to the right sheep.

The Gettier problem reveals that knowledge requires not just any justification but the right kind of connection between your evidence and the truth. In media terms: a news article might reach the right conclusion using the wrong evidence. The conclusion is true, the reasoning sounds plausible, but the actual evidence does not support it. Good epistemology demands that the connection between evidence and conclusion be genuine.

Worked Example: Running a Claim Through the Three Conditions

Imagine you glance at a wall clock reading 2:00 and form the belief 'It is 2:00.' It happens to be exactly 2:00, and you had good reason to trust a normally reliable clock. Believed, true, justified — surely knowledge? Now add Bertrand Russell's classic twist (from Human Knowledge, 1948): the clock stopped exactly twelve hours ago and has been frozen at 2:00 the whole time. You are right only by luck; your justification connected to a broken clock, not to the actual time. That is a Gettier case in miniature.

The table below runs the single claim 'It is 2:00' through four scenarios:

The last row is the hard one: every classical box is checked, yet we hesitate to call it knowledge because the link between evidence and truth is accidental. This is exactly the gap Edmund Gettier exposed, and it is why later philosophers proposed a fourth requirement — often a 'no false assumptions' clause or a demand that the belief be reliably connected to the fact — to repair the definition.