Level 1 · Module 5: True, Not True, and In Between · Lesson 3

Reasons and Proof

conceptargument-reasoning

When you believe something, you should be able to say why. A reason is the “because” behind what you believe. Some reasons are strong and some are weak — and learning to tell the difference is one of the most useful things a person can do.

Building On

Evidence

In our first lesson, we learned that evidence helps you figure out whether something is true. Now we’re going deeper: what counts as a good reason, and what doesn’t?

Why It Matters

Imagine someone tells you, “Dogs are better than cats.” Okay — but why? If they say, “Because dogs can be trained to help people who are blind,” that’s a reason. It might not prove dogs are “better” overall, but at least it’s something you can think about.

Now imagine they say, “Dogs are better because I like them more.” That’s not really a reason dogs are better — it’s just a statement about what that person prefers. It tells you about them, not about dogs.

Every day, you make decisions and form beliefs. The question is whether those beliefs are sitting on solid ground or on sand. Reasons are the ground. Without them, your beliefs blow over the first time someone pushes back.

This isn’t just about school or being smart. It’s about being the kind of person who thinks before they speak and can explain themselves clearly. That kind of person gets listened to.

A Story

The Case of the Missing Sandwich

At lunch on Tuesday, Owen opened his lunchbox and his sandwich was gone. Everything else was there — the apple, the crackers, the juice box — but no sandwich. Owen was upset. He looked around the cafeteria.

His classmate Brianna was eating a peanut butter and jelly sandwich. Owen’s sandwich was peanut butter and jelly. “Brianna took my sandwich!” Owen told his friend Wei. Wei looked over. “How do you know?” he asked. “Because she’s eating peanut butter and jelly, and mine is missing!” Owen said, as if that settled it.

Wei thought about that for a moment. “But a lot of people eat peanut butter and jelly,” he said. “That’s not really proof. Did you see her take it?” Owen hadn’t. “Did anyone see her near your lunchbox?” No one had. “Is her sandwich in a bag or on a napkin?” It was in a bag — a bag with her name written on it in marker.

Owen felt his face get warm. He had almost accused Brianna of stealing based on one coincidence: they liked the same kind of sandwich. That wasn’t a reason. That was a guess dressed up as a reason.

After lunch, Owen found his sandwich in his backpack. He’d put it in the wrong bag that morning while he was half asleep. He was really glad Wei had asked those questions before Owen had said anything to Brianna. One sloppy reason, believed too quickly, had almost caused real harm to someone who hadn’t done anything wrong.

Vocabulary

Reason
The “why” behind what you believe. A reason explains what makes you think something is true.
Proof
Strong evidence that shows something is true or false. Proof is harder to argue with than a guess or a feeling.
Coincidence
When two things happen at the same time by chance, not because one caused the other. Brianna eating PB&J on the same day Owen lost his was a coincidence.
Accuse
To say someone did something wrong. Accusing someone is serious and should only be done with good reasons.
Conclusion
What you decide is true after looking at the evidence. A good conclusion is based on strong reasons, not just feelings or guesses.

Guided Teaching

Let’s play a game. I’ll give you a belief, and you try to come up with a reason for it. Ready?

“Exercise is good for you.” Why? There are lots of good reasons: it makes your heart stronger, it gives you energy, doctors have studied it and found that people who exercise live longer. Those are all reasons based on evidence.

Now try a trickier one: “Chocolate ice cream is the best flavor.” Can you give a reason for that? You might say “because it tastes the best.” But that’s really just restating your opinion. Someone who loves strawberry could say the exact same thing about strawberry. When your only reason is “because I like it,” that’s a preference, not proof.

That doesn’t mean preferences are bad. It’s fine to like chocolate best. You just need to know the difference between “this is my favorite” and “this is actually the best.” One is about you. The other is a claim about the world that needs real reasons.

In the story, what was Owen’s reason for thinking Brianna took his sandwich? She was eating the same kind. Is that a strong reason or a weak reason? It’s weak — because lots of people eat PB&J. One matching detail isn’t proof.

What questions did Wei ask that helped Owen think more carefully? Wei asked if Owen had seen Brianna take it, if anyone else had seen her near his lunchbox, and whose name was on the bag. Those questions were looking for real evidence.

Here’s a good habit to build: before you say something is true, ask yourself, “What’s my reason?” If your reason is strong, go ahead. If your reason is weak, say “I’m not sure, but I think...” And if you have no reason at all, maybe don’t say it yet.

Why is it especially important to have good reasons before you accuse someone of doing something wrong? Because accusing someone falsely can really hurt them. Once you say “she stole my sandwich,” other people might believe it, and that’s very hard to undo even if you’re wrong.

Pattern to Notice

When someone gives you a reason for something, ask yourself: “Is this a real reason, or is it just a feeling or a coincidence?” A real reason connects to evidence. A feeling is just a feeling, and a coincidence is just two things happening at the same time. All three exist, but only one of them is proof.

A Good Response

When someone tells you something and you want to understand better, try asking: “What makes you think that?” or “What’s your reason?” This isn’t rude — it’s how smart conversations work. And when someone asks you the same question, be ready with an honest answer.

Moral Thread

Honesty

Honest people don’t just say things — they can explain why they believe what they believe. Having reasons for what you say is part of being truthful, because it means you’ve actually thought about whether your words match reality.

Misuse Warning

A child could use “What’s your reason?” as a way to endlessly challenge people and avoid accepting things they don’t want to hear. If a parent says “time for bed” and the child says “what’s your proof?” that’s not critical thinking — that’s stalling. This skill is for figuring out what’s true, not for arguing with every instruction you don’t like.

For Discussion

  1. 1.What’s the difference between a strong reason and a weak reason?
  2. 2.In the story, what would have happened if Owen had accused Brianna without checking?
  3. 3.Can you think of a time you jumped to a conclusion without enough evidence? What happened?
  4. 4.Is “everyone says so” a good reason? Why or why not?
  5. 5.What’s the difference between a reason and an excuse?
  6. 6.Why do you think Wei asked questions instead of just saying “You’re wrong”?
  7. 7.When is it most important to have really good reasons before you say something?

Practice

Reasons Detector

  1. 1.With a parent, take turns making claims and then giving reasons. The listener decides if the reason is strong, weak, or just a feeling.
  2. 2.Example: “Cats are good pets (claim) because they’re easy to take care of (reason).” Is that strong, weak, or a feeling? (Fairly strong — there’s real evidence cats need less daily care than some other pets.)
  3. 3.Example: “Monday is the worst day (claim) because I don’t like going back to school (reason).” Strong, weak, or feeling? (That’s a feeling. It’s real for you, but it’s not a reason Monday is actually worse than other days.)
  4. 4.Try to come up with three claims with strong reasons and three claims where the reason is really just a feeling. See if your partner can sort them correctly.

Memory Questions

  1. 1.What is a reason?
  2. 2.Why was Owen’s reason for thinking Brianna took his sandwich a weak reason?
  3. 3.What is a coincidence?
  4. 4.What’s the difference between a preference and a reason?
  5. 5.What questions did Wei ask that helped Owen think more carefully?
  6. 6.Why is it especially important to have good reasons before accusing someone?

A Note for Parents

This lesson introduces the basics of reasoning without using that intimidating word much. The key concept is that believing something should come with a “because.” You can reinforce this naturally in daily life: when your child makes a claim, sometimes ask “What makes you think that?” in a curious tone, not a challenging one. And when you make claims yourself, offer your reasons. Children model what they see more than what they’re told. The sandwich story also introduces an important real-world application: the danger of accusing someone without evidence. This is a lesson that pays dividends for years.

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