7.2 Knowledge

The Traditional Definition of Knowledge

Knowledge is one of the central topics in epistemology, and the question sounds deceptively simple: what does it mean to truly know something? Plato offered an answer that has shaped the debate for over two thousand years. He defined knowledge as justified true belief (JTB), and while most philosophers agree this definition captures something important, it turns out to have a surprising vulnerability.

Components of Plato's Definition

Plato's JTB definition has three conditions, and all three must be met for something to count as knowledge:

1. Truth — The proposition must actually be true. It has to match reality. You can't "know" something that's false. If you believe the Earth is flat, that's not knowledge, no matter how confident you are.

2. Belief — You must sincerely accept the proposition. If a statement happens to be true but you don't believe it, you can't be said to know it. For example, if someone tells you the correct answer on a test but you think they're lying, you don't know the answer even though you heard it.

3. Justification — You need good reasons or evidence for your belief. A lucky guess that turns out to be true doesn't count as knowledge. If you believe it's raining because you looked out the window and saw rain, that's justified. If you believe it's raining because you flipped a coin, that's not.

Each condition is necessary (you need all three), and together they were traditionally thought to be sufficient (having all three was enough). That second claim is exactly what the Gettier problem attacks.

The Gettier Problem

In 1963, Edmund Gettier published a short paper that changed epistemology. He showed that a person can have a justified true belief and still, intuitively, not have knowledge. These scenarios are called Gettier cases, and they all share a common structure: the belief is true, and the person has good reasons for holding it, but the belief is only true by luck or coincidence rather than because of the justification.

Analysis of a Gettier Case

Here's Gettier's most famous example, broken down step by step:

1. Smith and Jones both apply for the same job.
2. Smith has strong evidence that Jones will get the job (the company president told him so). Smith also knows Jones has ten coins in his pocket.
3. Smith reasons: "The person who will get the job has ten coins in his pocket."
4. Surprise: Smith gets the job, not Jones.
5. By sheer coincidence, Smith also happens to have ten coins in his own pocket, though he didn't know this.

Now check the JTB conditions for Smith's belief that "the person who will get the job has ten coins in his pocket":

• True? Yes. Smith got the job, and Smith does have ten coins in his pocket.
• Believed? Yes. Smith genuinely believed this proposition.
• Justified? Yes. He had strong evidence (the president's testimony plus his knowledge of Jones's coins).

All three conditions are satisfied. But does Smith really know this? Most people's intuition says no. His belief landed on the truth by accident. His justification pointed toward Jones, but the belief turned out to be true because of facts about Smith that he wasn't even aware of.

This is the core of the Gettier problem: JTB appears to be necessary for knowledge, but it's not sufficient. Something extra seems to be required.

Responses to the Gettier Problem

Philosophers have proposed various ways to patch the JTB definition. One of the most straightforward is the "no false lemmas" condition.

The No False Lemmas Condition

This approach adds a fourth requirement: your justified true belief counts as knowledge only if it was not inferred from any false belief. A "lemma" here just means a step in your reasoning.

In the Smith and Jones case, Smith's reasoning depended on the false belief that Jones would get the job. Under the no false lemmas condition, Smith's belief doesn't qualify as knowledge because it was built on that false step.

Strengths:

• It handles the classic Gettier cases cleanly, including the Smith and Jones example.
• It preserves the intuition that knowledge shouldn't rest on false foundations.

Limitations:

• It may be too strict. Sometimes a belief is inferred partly from a false premise, but the false premise is irrelevant to why the belief is true. In those cases, we might still want to say the person has knowledge, yet this condition would rule it out.
• It may not cover all Gettier-style cases. Philosophers have constructed scenarios where someone's belief isn't inferred from a false premise but is still only true by coincidence (for instance, cases involving misleading evidence from a normally reliable source).

The Gettier problem remains an open area of debate. No single proposed solution has gained universal acceptance, which is part of what makes it such a productive problem in epistemology.

Approaches to Knowledge

Beyond the question of how to define knowledge, epistemologists disagree about how we acquire it. Four major perspectives frame this debate:

• Empiricism holds that knowledge comes primarily from sensory experience. Observation and experimentation are the main tools. Think of the natural sciences: you learn about the world by looking at it, measuring it, and testing hypotheses against what you find.
• Rationalism holds that reason and innate ideas are a genuine source of knowledge. Some truths can be grasped through pure thought, independent of experience. Mathematical proofs are a classic example: you don't need to go out and observe anything to know that $2 + 2 = 4$.
• Skepticism questions whether certain knowledge is possible at all. Skeptics challenge the reliability of both our senses and our reasoning. This doesn't necessarily mean skeptics believe we know nothing, but they push us to examine how confident we should really be.
• Fallibilism accepts that our beliefs and knowledge claims might turn out to be wrong. Even well-justified beliefs can be revised in light of new evidence. Fallibilism emphasizes that inquiry is ongoing and that intellectual humility matters.

Types of Knowledge

Philosophers also distinguish knowledge by its relationship to experience:

• A priori knowledge is independent of experience. You can know it through reasoning alone. Mathematical truths ($7 + 5 = 12$) and logical principles (nothing can be both true and false at the same time) are standard examples.
• A posteriori knowledge depends on experience. You acquire it through observation or empirical investigation. Knowing that water boils at 100°C at sea level, or that Paris is the capital of France, requires some contact with the world beyond pure thought.

The line between these two types connects back to the empiricism vs. rationalism debate: empiricists tend to emphasize a posteriori knowledge, while rationalists argue that a priori knowledge is more foundational.