Gettier problem

The Gettier problem is a puzzle in philosophy that questions what it really means to "know" something. For a long time, many people believed that knowledge was simply a combination of three things: a belief that is true and justified. This means that if you believe something, have good reasons for believing it, and it turns out to be true, then you must have knowledge.^[1][2] But in 1963, a philosopher named Edmund Gettier showed that this might not always be enough. He gave examples where someone had a belief that was both true and justified, but it did not feel like they truly had knowledge.^[3]

The classical definition of knowledge

One of Gettier’s examples involved two people, Smith and Jones. Smith has strong evidence that Jones will get a job and that Jones has ten coins in his pocket. So Smith believes, “The person who will get the job has ten coins in their pocket.” But in a surprise twist, Smith actually gets the job instead, and he also happens to have ten coins in his pocket. His belief turned out to be true, and he had a good reason for it, but it was only true by accident. This shows that even when a belief is true and justified, it might still not count as real knowledge if it happens just by chance. This kind of situation is called “epistemic luck.”^[4]

To solve this problem, some philosophers suggested adding extra rules to the definition of knowledge. One idea is called the "no false lemmas" rule. This means that your belief should not be based on any false steps or wrong facts, even if your final conclusion is correct.^[5][6] Others, like Alvin Goldman, suggested that your belief must come from a process that usually leads to the truth, something called a reliable method.^[7] Another idea, from Robert Nozick, says that your belief should “track the truth,” meaning that if the belief were false, you would not believe it in the first place.^[8] There are even more theories. One is the causal theory, which says that there needs to be a direct link between the truth and your belief.^[9] Another is called virtue epistemology, which says knowledge comes from using good thinking habits, like careful reasoning and being open-minded, instead of just getting lucky.^[10][11]

Even with all these new ideas, people have come up with more tricky examples, called Gettier-style problems, that still do not fit neatly into these updated definitions. One famous example is the “fake barn” story. Imagine you are driving in the countryside and see a real barn. You believe, “That is a barn,” and you are right. But you do not know that all around you are fake barn lookalikes. You happened to look at the one real barn. Your belief is true and reasonable, but again, it seems like you were just lucky, so do you really know it was a barn?^[12]

The Gettier problem does not just matter to philosophers. It has also influenced areas like artificial intelligence, where machines need to do more than just have correct answers, they need to explain how they got them.^[13] It also affects law, where it’s important to think about whether someone’s belief or judgment was based on solid evidence or just luck.^[14] Some modern philosophers, like Timothy Williamson, say maybe the whole idea of trying to define knowledge by breaking it into smaller parts like belief, truth, and justification is the wrong approach. Instead, they say knowledge should be seen as its own basic idea, not something that has to be built from other parts. This idea is called knowledge-first epistemology, and it tries to avoid the confusing situations that the Gettier problem brings up.^[15]