The Gettier Problem: True Justified Belief without Knowledge

The Problem

Suppose you look outside the window one day and see a figure shoveling snow. You recognize the coat and silhouette and think, “Oh, my dad’s shoveling snow.” However, that person isn’t actually your father, but your next-door neighbor. He owns the same winter jacket as your father and is a similar height. Yet, coincidentally, on the other side of the house, your father is in fact shoveling snow. Can you say that you knew your dad was shoveling snow?


In this situation, your belief that your dad was shoveling was justified - your neighbor looks very similar to your dad - and it was true - your dad was, in fact, shoveling snow on the other side of the house - but you cannot say you knew that your dad was shoveling snow. This example is what is known as a Gettier problem.

Gettier Problem

A Gettier problem is any example that demonstrates that an individual can satisfy the classical analysis of knowledge - justified true belief - without possessing knowledge.

How It Works

Philosophers have long attempted to give an analysis of knowledge by outlining the necessary and sufficient conditions that one must satisfy to be able to know a fact. Necessary conditions are requirements that a concept must have to be called that thing it is. For example, being divisible by two is a necessary condition of being an even number. On the other hand, sufficient conditions are qualities whose presence automatically qualifies a thing to be called the object in question. Being a beagle is a sufficient condition of being a dog, and so is being a pug, or golden retriever, or dalmatian. 

Ancient Greek Philosopher Plato was the first to propose the classical analysis of knowledge, which defines knowledge as a justified true belief. This is known as the JTB theory of knowledge. A belief is any claim that you accept. A true belief is any claim you accept that corresponds to how things are in the world, and a justified true belief is a true belief that has proper evidence. In terms of necessary and sufficient conditions, all of these parts are necessary for knowledge, but none of them alone is sufficient to count as knowledge. For example, you may believe that aliens are real, but until your belief is justified and true, it is not knowledge.

The Gettier problem is named after American philosopher Edmund Gettier, who in 1963 presented two famous counterexamples to the JTB account of knowledge. The most well-known case is about two men who are applying for a job: Jones and Smith. Smith has been assured that Jones will get the job by the company president, and he has counted that Jones has 10 coins in his pocket. He concludes that “The man who will get the job has ten coins in his pocket.” However, Smith himself unknowingly has 10 coins in his pocket and gets the job. In this case, Smith’s belief that the man who will get the job has ten coins in his pocket is true, and he is justified in believing it; yet few would say that Smith knows this fact.

Gettier problems arise when there exists a relapse in the relationship between justification and truth. You are justified in believing your dad is shoveling snow because you see someone who strongly resembles him outside. However, the truth of your belief is not connected to what you see. It is only coincidentally true.

Philosophers have tried endlessly to adapt and revise the classical theory of knowledge to avoid the Gettier problem, often by attempting to find the “fourth condition” of knowledge to add to the JTB theory. One of the simplest solutions is the no false beliefs condition. This account adds an addendum that knowledge cannot rest on any false beliefs. Therefore, your true justified belief that your dad is shoveling snow does not count as knowledge because it rests on the false belief that your neighbor is your dad. The issue with this solution is that there are cases of knowledge that do rest on false beliefs yet are knowledge all the same. For example, consider a detective who interrogates ten people who say they are witnesses to a crime. However, one of these ten people is lying. Therefore, when the detective concludes who committed the crime based on testimonial evidence, she will include a false belief that the one lying witness saw the crime. Yet, this single false belief does not invalidate the detective’s knowledge because of the large body of truthful witnesses who also saw the crime. An account of knowledge should not become overly demanding, discrediting everyday intuitions in order to surmount the Gettier problem. The no false belief condition seems to go too far.

So What?

The Gettier problem reminds us that a definition of knowledge cannot and should not require complete certainty. Although any account of knowledge that does not bind truth and justification together may encounter Gettier-style counterexamples, this may be an inescapable problem. We shouldn’t turn to radical skepticism and claim that we know nothing. Instead, consider the ways we use knowledge in our daily lives. Knowledge serves an important evolutionary function, whether it’s the location of a beehive on a mountain trail or that there’s a measles outbreak in Philadelphia. Therefore, we need a reliable process for deciding when to trust our senses and others’ testimony, even if this process does not result in a foolproof analysis every time.

Think Further

  1. Should we search for a definition of knowledge? Why or why not?
  2. Why should we not define knowledge as certainty? 
  3. Do Gettier problems threaten everyday knowledge claims? How so?


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Learn More

  1. Hetherington, Stephen. “Gettier Problems.” Internet Encyclopedia of Philosophy.
  2. Crashcourse. “The Meaning of Knowledge: Crash Course Philosophy #7.” Youtube, 21 March 2016.
  3. Zagzebski, Linda. “The Inescapability of Gettier Problems.” Philosophical Quarterly, vol. 44, no. 174, 1994, pp. 65-73.
  4. Wireless Philosophy. “PHILOSOPHY – Epistemology: Analyzing Knowledge #3 (Causal and Reliabilist Theories).” Youtube, 11 March 2016.