When "I Know" Doesn't Mean the Same Thing

You’re sitting in class, and your friend whispers, “Do you know what time lunch is?” You glance at the clock, see 11:45, and nod. You know.

Now imagine you’re about to take a test that determines your whole grade. Someone asks, “Do you know the quadratic formula?” You’ve studied it, but suddenly you’re not so sure. Maybe you don’t really know it after all.

Here’s the strange thing philosophers noticed: in both cases, you have the same evidence, the same memory, the same training. So why does “I know” feel right in one moment and wrong in the next? Is knowledge something that can come and go depending on how you’re feeling? Or is something else going on?

Welcome to the debate about epistemic contextualism — a weird and slippery idea about the word “know” itself.

The Puzzle That Started It All

Let’s start with something that’s bothered philosophers for centuries. Consider this argument, which we’ll call the Skeptical Argument:

I don’t know that I’m not a brain in a vat being fed fake experiences.
If I don’t know that I’m not a brain in a vat, then I don’t know that I have hands.
So, I don’t know that I have hands.

This argument is a puzzle because:

Premise 1 seems true. How could you prove you’re not a brain in a vat? Any test you run would just be another set of experiences the vat-scientists could feed you.
Premise 2 also seems true. If I don’t know whether I’m a disembodied brain being tricked, then how can I claim to know anything based on my senses? If my hands could be an illusion, I can’t really say I know I have them.
But the conclusion seems obviously false. Of course I know I have hands! I’m looking at them right now.

Something has to give. But what?

Most people think there are only three options: (a) accept that we don’t know very much (skepticism), (b) reject premise 2 (which means rejecting a very natural principle about how knowledge works), or (c) reject premise 1 (which means claiming you do know you’re not a brain in a vat — a hard sell).

None of these options look great. But a group of philosophers noticed a fourth possibility — one that’s both clever and strange.

The Contextualist Move

Here’s the idea: maybe the word “know” doesn’t have a fixed meaning. Maybe, like words such as “flat,” “tall,” or “here,” what “know” means changes depending on the situation.

Think about the word “flat.” If a friend says “my driveway is flat,” and you’re talking about whether you can skateboard on it, that’s true enough. But if you’re a carpenter checking whether a surface is perfectly level, you might say the same driveway isn’t flat at all. Who’s right? Both — because “flat” means different things in different conversations. The standard for flatness shifts.

Now, what if “know” works the same way? In ordinary, everyday conversations, the standard for knowing something is pretty low. You glance at the clock and say “I know what time lunch is” — that’s true, given the standards operating in that context. But when a skeptic starts talking about brains in vats, the standards get jacked way up. In that context, “I know I have hands” becomes false — because at those super-high standards, you’d have to rule out every possibility, including crazy skeptical ones.

The key move: the skeptic’s argument changes the context. By the time you reach the conclusion, you’re evaluating “I know I have hands” against impossibly high standards. So the conclusion is true — but only in that special, high-stakes context. Your ordinary claim to know you have hands, made in everyday contexts, remains perfectly true.

This is the core of epistemic contextualism (EC for short). It’s not a theory about what knowledge is. It’s a theory about the word “know” — specifically, that its meaning shifts with context.

Everyday Cases That Support the Idea

The skeptic’s argument is one thing. But contextualists say we can see the same pattern in ordinary life, without any brains in vats.

Imagine two people at an airport. Smith looks at his printed itinerary and says, “I know this flight stops in Chicago.” That seems reasonable enough — the itinerary is printed on official letterhead, and airlines don’t usually make mistakes on their schedules.

But Mary and John overhear this. They have a very important business meeting in Chicago — if they miss it, they’ll lose their jobs. Mary says, “That itinerary could have a misprint. They could have changed the schedule. Smith doesn’t really know the flight stops in Chicago.”

Now here’s the puzzle: Smith has the same evidence Mary and John have. Nothing about the itinerary has changed. Yet Smith says he knows, and Mary says he doesn’t. Who’s right?

A contextualist says: both are right. Smith’s context has low stakes, so the standard for knowing is low. Mary and John’s context has high stakes, so the standard is high. Smith truly knows (in his context) that the flight stops in Chicago. And Mary and John are right to deny that he knows (in their context) because at their higher standard, he doesn’t.

Notice: this isn’t saying that Smith both knows and doesn’t know. It’s saying that the word “know” expresses different claims in different contexts — just like “flat” does. The sentence “Smith knows the flight stops in Chicago” expresses one proposition when Smith says it, and a different (more demanding) proposition when Mary denies it. They’re not really disagreeing, because they’re not talking about the same thing.

How Contextualists Explain the Shift

Different philosophers have different ideas about what exactly determines the standards. Here are a few:

Stewart Cohen thinks the standards shift based on what possibilities are salient — what possibilities you’re paying attention to. When someone mentions the possibility of a misprint, that possibility becomes salient, and now you need evidence good enough to rule that out. When a skeptic mentions brains in vats, that possibility becomes salient, and now you need evidence good enough to rule that out. In ordinary life, those weird possibilities aren’t on anyone’s mind, so the standards stay low.

David Lewis had a similar but more dramatic view. He said that knowing something means your evidence eliminates every possibility where you’d be wrong. That sounds like it would make knowledge impossible. But Lewis said the word “every” is restricted to possibilities that count — that are “properly” considered. And here’s the kicker: once you pay attention to a possibility (like the brain-in-vat possibility), it’s no longer properly ignored. So knowledge is “elusive” — “examine it, and straightway it vanishes.” The moment an epistemologist asks whether you really know something, they’ve changed the standards and made that knowledge disappear.

Keith DeRose connects knowledge to sensitivity — roughly, whether you’d still believe something if it were false. In ordinary contexts, your belief that you have hands is sensitive: if you didn’t have hands, you’d notice. But your belief that you’re not a brain in a vat is insensitive: even if you were a brain in a vat, you’d still believe you weren’t. So when the skeptic raises this insensitivity, the standards go up, and your ordinary knowledge claims stop being true.

Each of these views is different, but they share the same basic idea: the word “know” shifts meaning depending on context.

Problems and Pushback

Not everyone is convinced. Critics raise several objections.

Does contextualism really answer the skeptic? Ernest Sosa argues that contextualism misses the point. When philosophers ask “Do we know anything?” they’re not asking about what we can say in ordinary conversation. They’re asking a serious, philosophical question — and that question is being asked in a philosophical context, not an everyday one. If contextualism is right, then in the philosophical context (where we’re thinking about brains in vats), the skeptic’s conclusion is true. But that’s exactly what the anti-skeptic wanted to deny. Contextualism just moves the bump in the rug.

The error theory problem. If “know” is context-sensitive in the way contextualists claim, why don’t ordinary speakers realize this? When I say “Kansas is flat” and you point out a small hill, I’ll say “Oh, I meant relatively flat.” But when a contextualist says “Smith knew in his context but not in ours,” people often feel confused or resistant. Why would we be so blind to the context-sensitivity of “know” if it’s really there?

Some contextualists admit: we are blind to it. It takes philosophical reflection to notice. But critics say this is too convenient — the contextualist is claiming that ordinary speakers are systematically mistaken about what they mean when they say “I know.”

Linguistic evidence. Jason Stanley points out that “know” doesn’t behave like other context-sensitive words. You can say “very tall” or “sort of flat,” but you can’t say “very know” or “sort of know.” You can clarify what you mean by “flat” by saying “I mean relatively flat,” but there’s no natural way to clarify what you mean by “know.” This suggests “know” might work differently from words like “flat” and “tall.”

The disagreement problem. If two people are in different contexts, and one says “Smith knows” and the other says “Smith doesn’t know,” they seem to be disagreeing. But if contextualism is right, they’re not — they’re talking about different things. But they feel like they’re disagreeing. They don’t say “Oh, well, you’re using different standards, so we’re both right.” They argue. This suggests that the word “know” isn’t shifting meaning the way contextualists think.

Alternative Views

Because of these problems, other philosophers have proposed alternatives:

Subject-Sensitive Invariantism says that whether you know really does depend on what’s at stake for you, the knower — not just on what standards the person talking about you has. On this view, if you have a huge amount riding on whether the flight stops in Chicago, you might genuinely not know, even if someone with less at stake would know with the same evidence. Knowledge itself depends on practical stakes.

Contrastivism says that “knows” is a three-place relation: you don’t just know that p; you know that p rather than q. What changes across contexts is which contrast is relevant. In the airport case, Smith might know the flight stops in Chicago rather than some other city, but not know it rather than a misprinted itinerary.

Relativism says that the truth of “Smith knows that p” depends on the standards of whoever is judging the claim — even if they weren’t present when the claim was made. This is different from contextualism, because it allows that the same sentence can be true for one person and false for another, even if neither person’s context has changed.

Each of these views tries to capture what seems right about contextualism (that our knowledge judgments vary in puzzling ways) while avoiding its problems.

Why This Matters

You might be thinking: “So what? Why should I care whether ‘know’ is context-sensitive?”

Here’s why: we use the word “know” all the time. We say we know things. We rely on other people’s knowledge. We make decisions based on what we think we know. If the word “know” shifts meaning depending on context — and especially if we’re often unaware of those shifts — then we might be misunderstanding each other systematically.

When your teacher says “You should know this for the test,” do they mean the same thing as when your friend says “I know where we’re going”? When a witness in court says “I know he was there,” should we hold them to the same standard as when someone says “I know what I want for dinner”?

The debate over contextualism isn’t just a technical squabble among philosophers. It’s a debate about how we communicate what we’re sure of, and whether we’re as sure as we think we are. The answer isn’t settled — philosophers still argue about it. But the very fact that they argue shows something interesting: “knowledge” is a more slippery idea than we usually realize.

Key Terms

Term	What it does in this debate
Contextualism	The view that the word “know” shifts meaning depending on the speaker’s context
Epistemic standard	How strong your evidence needs to be for something to count as “knowledge” in a given context
Skeptical hypothesis	A scenario (like being a brain in a vat) that, if true, would mean you don’t know most things
Salience	Which possibilities are being paid attention to — contextualists think this affects the standard for knowing
Invariantism	The opposing view that “know” has a fixed meaning, no matter the context
Closure principle	The idea that if you know something, and you know that thing implies something else, then you know that something else too

Key People

Stewart Cohen — Contemporary philosopher who argues that “know” inherits context-sensitivity from “justified,” and that the standards shift based on which possibilities are salient.
David Lewis — Influential philosopher who proposed that knowledge requires eliminating every possibility where you’d be wrong, but that “every” is restricted to possibilities we’re actually thinking about.
Keith DeRose — Key defender of contextualism who connects knowledge to “sensitivity” (whether you’d still believe something if it were false) and argues that skeptical arguments work by raising the standards.
Ernest Sosa — Critic of contextualism who argues that it doesn’t really answer the skeptic, because in philosophical contexts the skeptic’s conclusion is still true.
Jason Stanley — Critic who argues that linguistic evidence (like the fact that you can’t say “very know”) shows “know” isn’t genuinely context-sensitive.

Things to Think About

If “know” really is context-sensitive, does that mean we should be less confident when we say we know things? Or does it just mean we should be more careful about which context we’re in?
Think of a time when you said you “knew” something, then later realized you were wrong. Would contextualism help explain why you felt confident at the time? Or does that just show you were mistaken, period?
If two people are in different contexts, and one says “I know it’s raining” while the other says “You don’t know it’s raining,” are they genuinely disagreeing? Or are they just talking past each other? How could you tell?
The contextualist says that when the skeptic raises the brain-in-vat hypothesis, the standards for knowing go up. But should they? If our evidence hasn’t changed, why should mentioning a weird possibility make a difference to whether we “really” know?

Where This Shows Up

In courtrooms: Lawyers often argue about whether a witness “knows” something or just “thinks” it. The standards might shift depending on how important the case is.
In science: Scientists talk about what we “know” about climate change, vaccines, or the age of the universe. But the standards for “knowing” in science might be different from everyday standards.
In online arguments: When people say “I know you’re wrong” or “You don’t know what you’re talking about,” they might be operating with different standards without realizing it.
In your own life: The next time someone asks “Do you know that for sure?” notice how the answer changes depending on what’s at stake. Are you meeting different standards, or are you just being honest about uncertainty?