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Year 10 Philosophy

What Can We Really Know?

You think you know things. But how do you know that you know them? Welcome to epistemology.

The Big Question

How do you know what you think you know?

This branch of philosophy -- epistemology -- questions the very foundations of knowledge, truth, and belief.

Ways of Knowing

How do we acquire knowledge? Philosophers (and the IB Theory of Knowledge course) identify several distinct ways of knowing. Each has strengths and limitations.

Reason

Using logic to work things out. "All humans are mortal. Socrates is human. Therefore, Socrates is mortal."

Limitation: Logic can be valid but still wrong if the starting premises are false.

Perception

Using your senses (sight, hearing, touch, taste, smell) to observe the world directly.

Limitation: Senses can be deceived. Optical illusions, hallucinations, mirages.

Emotion

Feelings that guide understanding. You "know" your friend is upset by empathising with their mood.

Limitation: Emotions are subjective and can cloud rational judgment.

Language

Words shape how we think. The language you speak actually affects how you perceive the world.

Limitation: Language can manipulate, mislead, and oversimplify complex truths.

Intuition

"Gut feeling." You sometimes just know something is true without being able to explain why.

Limitation: Intuition is often just pattern recognition that can be wrong -- and we can't verify it.

Testimony / Authority

Believing something because someone told you, especially an expert or trusted source.

Limitation: Authorities can be wrong, biased, or lying. Appeals to authority are a logical fallacy.

Think About It
  • • Which way of knowing do you trust most? Why?
  • • Can you think of a time your senses deceived you?
  • • Is there anything you "know" purely through intuition that you can't prove?

The Problem of Certainty

Our minds are powerful, but deeply flawed. Here are some ways your brain tricks you into being certain about things that are wrong.

Optical Illusions

Your eyes tell your brain something that isn't true. Two lines look different lengths even though they're identical. A static image appears to move. If your senses can be wrong about something this basic, what else might they be wrong about?

False Memories

Research by Elizabeth Loftus showed that people can be made to "remember" events that never happened. In one study, 25% of participants came to believe a completely fabricated childhood memory was real. Your memories are not recordings -- they're reconstructions.

Cognitive Biases

Your brain takes mental shortcuts that systematically distort your thinking:

Confirmation Bias

You notice evidence that supports what you already believe and ignore evidence that contradicts it.

Dunning-Kruger Effect

People who know very little about a topic tend to overestimate their knowledge. Experts tend to underestimate theirs.

Availability Heuristic

You judge how likely something is based on how easily you can think of examples. (Shark attacks seem common because they're in the news.)

Anchoring Bias

The first piece of information you receive disproportionately influences your judgment, even if it's arbitrary.

Think About It
  • • Can you think of a time you were absolutely certain about something and turned out to be wrong?
  • • If our memories can be false, how reliable is eyewitness testimony in court?
  • • How do you know your current beliefs aren't being distorted by confirmation bias right now?

Plato's Cave: The Most Famous Philosophy Thought Experiment

Written around 380 BCE, Plato's Allegory of the Cave is one of the most influential ideas in the history of thought.

The Allegory

Imagine people who have lived their entire lives chained inside a dark cave, facing a wall. Behind them, a fire casts shadows of objects onto the wall.

These shadows are all the prisoners have ever seen. To them, the shadows ARE reality. They name the shadows, discuss them, and believe they understand the world.

One prisoner breaks free and walks outside the cave. At first, the sunlight blinds them. Gradually, they see the real world: trees, rivers, the sun itself. They realise that everything they believed was real was just a shadow -- a pale imitation of true reality.

They return to the cave to tell the others. But the other prisoners think they've gone mad. The shadows are all they've ever known, and they refuse to believe there's anything else.

The Cave =

Our limited experience and assumptions about reality

The Shadows =

What we think we know (but may only be partial truths or illusions)

The Sunlight =

True knowledge and understanding (gained through philosophy and critical thinking)

Think About It
  • • What is YOUR cave? What "shadows" might you be mistaking for reality?
  • • Is social media a modern version of Plato's Cave?
  • • Why do the prisoners reject the freed prisoner's truth? What does this say about human nature?

Epistemology Today: Knowledge vs Belief vs Opinion

In the age of fake news, misinformation, and AI-generated content, understanding the difference between knowledge, belief, and opinion has never been more important.

Knowledge

A justified, true belief. You believe something, it is actually true, and you have good reasons for believing it.

Example: "Water boils at 100 degrees Celsius at sea level." (Scientifically verified)

Belief

Something you hold to be true, but which may or may not be supported by evidence. Can be personal, religious, or cultural.

Example: "There is life on other planets." (Possible but unverified)

Opinion

A personal view or judgment that doesn't claim to be factual. Opinions can't be proven true or false.

Example: "Chocolate ice cream is the best flavour." (Subjective preference)

Fake News and Epistemology: How to Evaluate Truth Claims

When you see a claim online, use this epistemological checklist:

1

Source: Who is making this claim? Do they have expertise? What is their motivation?

2

Evidence: What evidence supports this claim? Is it peer-reviewed research, anecdote, or assertion?

3

Corroboration: Do other reliable, independent sources confirm this claim?

4

Bias check: Am I believing this because it's true, or because it confirms what I already think?

5

Falsifiability: Could this claim theoretically be disproven? If not, it may not be a knowledge claim at all.

Think About It
  • • Think of something you saw on social media recently. Apply the 5-step checklist. Does it hold up?
  • • Is scientific knowledge "true," or is it just the best explanation we have so far?
  • • Can AI-generated content create a "post-truth" world where we can no longer tell what's real?

Key Vocabulary

Epistemology

The branch of philosophy concerned with the nature, sources, and limits of knowledge.

Justified True Belief

The classical definition of knowledge: you believe it, it's true, and you have good reasons.

Cognitive Bias

A systematic error in thinking that affects judgments and decisions.

Empiricism

The view that knowledge comes primarily from sensory experience and observation.

Rationalism

The view that knowledge comes primarily from reason and logical thinking.

Falsifiability

The principle that a claim must be testable and potentially disprovable to count as scientific.

Knowledge Check

Test your epistemological thinking. These questions challenge you to examine how you know what you know.

Question 1

Which of the following best fits the definition of "knowledge" (justified true belief)?

Question 2

In Plato's Cave, the prisoners refuse to believe the freed prisoner. This is most similar to which modern phenomenon?

Question 3

You see a headline: "BREAKING: Scientists discover miracle cure for all cancers!" What is the FIRST question an epistemologically minded person should ask?

Question 4

A person says: "I saw it with my own eyes, so it must be true." What is wrong with this reasoning?

Question 5

The principle of falsifiability states that for a claim to be scientific, it must be possible to prove it wrong. Which of these claims is NOT falsifiable (and therefore not scientific)?

Key Concepts Summary