How Do We Really Know Things?

Critical Thinking: Ages 12+

How Do We Really Know Things? The Four Sources of Knowledge

Every single thing you believe came from somewhere. Let's become knowledge detectives and find out where!

When someone tells you something — "sharks never sleep," "your cousin got a new puppy," "it's going to rain tomorrow" — have you ever asked yourself: how do they know that? It turns out almost everything we know comes from just four places. Let's meet them.

👀Observation

🧪Experience

📚Accounts

🧠Inference

👀 1. Observation

Observing means noticing something with your senses — seeing, hearing, smelling, touching, or tasting — without it happening to you.

Example: You look out the window and see that it is raining. You didn't feel the rain — you just watched it. That's an observation.

🧪 2. Experience & Experiments

Experience is different — it happens to you or because of you. An experiment is when you test something on purpose to see what happens.

Example: You run outside and the rain actually gets you wet. Or you put an ice cube in the sun to test if it melts, and you watch it happen with your own hands.

📚 3. Collective Accounts

This is when we learn from other people's observations and experiences — through books, news, history, or someone telling us a story.

Example: You weren't alive during the dinosaurs, but a book tells you what scientists found by digging up bones. That's a collective account — it's real knowledge, but you should still ask: who wrote it, and how did they find out?

🧠 4. Logical Inference

Sometimes we can't observe, experience, or read about something directly — so we think it through instead. This is called inference, and detectives use it all the time! There are three special kinds.

🔵 Induction — Spotting a Pattern

You look at several examples, notice a pattern, and guess it will probably keep happening. The more examples you have, the stronger your guess — but it's still just a strong guess, not a certainty.

Example: Every marble you've pulled out of the bag so far has been red. So you guess the next one will probably be red too. Maybe! But you can't be 100% sure until you check every marble.

🟢 Deduction — Following the Rule

You start with things you know are true, and logic forces you to a conclusion. If your starting ideas are really true, the conclusion has to be true too.

Example: All birds have feathers. A robin is a bird. So a robin has feathers. If both starting facts are true, this conclusion can't be wrong!

🟣 Abduction — The Best Guess

You find some clues and pick the explanation that makes the most sense — even though other explanations are still possible.

Example: You come home and see muddy paw prints from the door to the kitchen. You guess your dog got outside and came back in. That's probably right — but maybe someone else's dog got in, or someone tracked in mud themselves. It's your best explanation, not a sure thing.

Careful, detective! A thought can follow all the rules perfectly and still be wrong. Imagine someone says: "All metal sinks in water. This spoon is metal. So this spoon sinks." The steps of thinking are lined up correctly — that's called being valid. But is the first idea even true? Nope — some metal boats float! When your starting idea is wrong, a perfectly "valid" thought can still lead you to a wrong answer. So always check: is the starting idea actually true, and does the thinking make sense?

Here's a big secret: just because a grown-up, a book, or someone with lots of followers says something, that doesn't automatically make it true. Ask yourself — did they see it? Did they experience it? Did they read it somewhere reliable? Or are they just guessing? And check it against the real world whenever you can.

One more thing: imagination, feelings, and stories can be wonderful — they just aren't the same as knowledge. It's fine to feel like your team will win, or to imagine a dragon lives in the mountains. Just remember: a fun idea isn't automatically a true one.

🕵️ Part 1: Which Source Is It?

Tap Observation, Experience, or Account for each sentence.

1. "I watched a rainbow appear in the sky after the rain stopped."

That's right! You noticed it with your eyes, but it didn't happen to your own body — that's an observation.

2. "I bit into a lemon and my whole mouth puckered up."

That's right! The sourness happened directly to you — that's experience.

3. "My grandma told me about a huge flood in her village when she was little."

That's right! You're learning about someone else's experience through their story — that's a collective account.

4. "My book about ancient Egypt says workers used ramps to build the pyramids."

That's right! Nobody alive today watched the pyramids get built — this comes from records and evidence historians collected. It's a collective account.

🧠 Part 2: Which Kind of Thinking Is It?

Tap Induction, Deduction, or Abduction for each sentence.

5. "The last nine marbles I pulled out were all red, so the next one is probably red too."

That's right! You spotted a pattern in several examples and guessed it continues — that's induction.

6. "All birds have feathers. A robin is a bird. So a robin has feathers."

That's right! Two true starting facts logically force this conclusion — that's deduction.

7. "I found muddy paw prints from the door to the kitchen, so I think my dog got outside and came back in."

That's right! You picked the best explanation for the clues, even though other explanations were possible — that's abduction.

8. "Every wells I've tested in this town so far has tasted a little salty, so wells around here are probably salty."

That's right! A pattern from several tested wells leads to a probable — not certain — conclusion about the rest. That's induction.

Next time you hear something and think "that's true!" — pause and ask: where did this come from? Did I see it, feel it myself, read it in a trustworthy account, or figure it out through induction, deduction, or abduction? Knowing the source is the first step to knowing what's real. 🔍