Rulers - thinking about knowledge and stealing

Thought Adventure no. 20

Equipment needed and preparation:

A standard classroom ruler and a less standard, more unique looking item(s).

Starting age: 5 years

Key concepts / vocabulary: steal, find, borrow, know, intention, property, ownership, permission

Subject links: PSHE and all knowledge-based subjects

Key controversies: When are you able to say that you know something? Are all cases of taking other people’s things stealing? What role does knowing play in stealing?


  • To know what you know and what you do not know, that is true knowledge.’ - Confucius
  • ‘I even felt guilty that I accidentally stole a Subbuteo catalogue, thinking it was free.’ - Julian Baggini

Critical thinking tool: Fallacy: Jumping to conclusions - In his excellent book A Rule book For Arguments, Anthony Weston identifies two fallacies as so common that he entitles them ‘The Two Great Fallacies’. The first is ‘generalising from incomplete information’ and the other is ‘overlooking alternatives’ (Google search ‘False dichotomy’). One jumps to conclusions when one makes a judgement before having all the facts. It is closely related to the inference-observation confusion and this is when someone infers generally from observations. Under normal circumstances children may well jump to conclusions if they were to see Sam with a pencil looking the same as one they lost.

Key Facilitation Skill: Questioning strategy: iffing - this enquiry is great for seeing how the questioning strategy iffing (a detailed account of iffing can be found in "The If Machine by Pete Worley) works. Imagine that you were you to come back into the classroom holding the ruler in the other hand and one of the children were to say, ‘It’s not the same ruler because you came back in holding it in the other hand.’ Given that it is possible you don’t even remember doing it, the simplest way to deal with this is to say (to the whole class and not just the speaker): ‘If I came back into the class holding the ruler in a different hand, does that mean that it is a different ruler or not?’

Session Plan:

Do: Take a standard ruler or similar object, of which you have many in the school, making sure that it has no distinguishing features.

Say: I have with me a ruler, as you can see.

Do: Step out of the room for a short period of time, taking the ruler with you then go into the classroom.

Task Question 1

  • Is this the same ruler?

Task Question 2

  • Do you know that it is the same ruler?

Nested Questions: 

  • If so, then how do you know? 
  • What is knowing? 
  • How do you know something? 
  • How do you know that you know something? 
  • Is there a difference between 'thinking you know something' and just 'knowing something'?


Do: Narrate the following scenario (like the narrator in Peppa Pig!) to the class and have the scene dramatised, either by some other staff members or by some children (see ‘Instant dramatisation’ on page x). Give the actor who is about to play ‘Jenny’ a pencil.

Say: Jenny has her ruler. She is very happy with her ruler. It is her favourite ruler. At some point in the day she loses it. Jenny is very upset to have lost her ruler. She goes to class upset that she has lost her ruler.

[Exit Jenny, leaving the pencil on the floor, ‘lost’]

Say: A little while later Sam comes along. He is annoyed because he forgot his ruler today. He is on his way to class and so needs a ruler to work with. Then, on the ground in front of him, he sees the ruler. ‘Perfect! Just what I need,’ he thinks to himself. Sam picks up the ruler and takes it to class with him, happy that he now has a ruler for the day. It’s a nice one too!

Task Question

  • Did Sam steal Jenny’s ruler?

Nested Questions

  • What is stealing?
  • Does knowing play a role in answering this task question? If so, what role does it play?
  • Can you steal something by accident? (See Baggini quote above)

Extension activities

  • You could repeat the scenario, the second time replacing the ruler with something less  standard and more unique-looking.
  • You could point out that the ‘standard’ rulers are school property and then return to the task question: Did Sam steal Jenny’s ruler?

General application

The opening stimulus (walking out of the room with a ruler and then walking back in again) has a wider application: you could use this stimulus with any object where you want the children to think about identity, or whether one or two things are the same thing. You could even ask one of the children (or do so yourself) to step out of the classroom and then step back in again, asking: ‘Is [insert name of person] the same person?’

Using the = sign

Another way to discuss identity in a way that all ages - including nursery - can join in, is to ask if two things are the same. You could write two words up on the board with an equals sign in between them and a question mark after. For example, ‘mind = brain ?’ Or, you could laminate two pieces of paper or card, one with ‘=‘ on and the other with ‘?’ on, then simply place items (such as water and ice) in the appropriate place, or write words on A4 paper or whiteboards. The idea is for the children to understand (and use) the ‘=‘ sign to mean ‘identical’, not ‘the answer’. Try these:

  • Odysseus = Ulysses ?
  • Square = [Square symbol] ?
  • 2 = 2 ?
  • 2 = 2 + 2 ?
  • Same = similar ?

Related Resources​

  • The If Machine: The Robbery
  • Once Upon an If: The Six Wise Men, Flat Earth, Honest Sa’id, The Island
  • The Philosophy Shop: The Pencil, Not Very Stationary Stationery (‘Rulers’ can be thought of as an extension to Michael Hand’s and A.C. Grayling’s contributions. Try dramatising Michael’s and Anthony’s sessions), The Adventures of Poppy The Bear, Knowing Stuff, Little Thea’s Tricky Questions
  • Thoughtings: How do you know that?

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