“And people are different from animals because they can have pictures on the screens in their heads of things which they are not looking at. They can have pictures of someone in another room. Or they can have a picture of what is going to happen tomorrow. Or they can have pictures of themselves as an astronaut. Or they can have pictures of really big numbers. Or they can have pictures of Chains of Reasoning when they’re trying to work something out.

And that is why a dog can go to the vet and have a really big operation and have metal pins sticking out of its leg but if it sees a cat it forgets that it has pins sticking out of its leg and chases after the cat. But when a person has an operation it has a picture in its head of the hurt carrying on for months and months.”