ELI5: Do you remember when you watched the lion king the other day? Well when Mufasa died you cried like a little bitch. Did mummy or daddy cry as well? No we didn't because we aren't little bitches. And what did it feel like to cry? You felt very sad didn't you? Well there are some people in the world, like mummy and daddy, who don't cry and can't feel sad at all. How would you explain to them how you felt when you watched Mufasa die? How would you explain to them, the feeling of sadness? It would be very hard wouldn't it? Well sometimes when we try to explain something, if we can't explain it directly we look to see what it's related to. For example, when you push on your eyeball what see becomes a little shaky and blurry. That means that whatever it is that you see has something to do with your eye ball. Now in the case of you trying to explain what it's like to feel sad to mummy and daddy, we can do something similar. In the same way we push on the eyeball to effect your vision, we can open up your skull, push on the grey stuff inside your skull, and it will make you feel sad. And every time we push on it in just the right spot, you feel sad. So that tells us that the grey stuff in your skull has something to do with you feeling sad. We might now ask what the grey stuff has to do with feeling sad? After all, you didn't even know there was grey stuff in your head until I just told you. Yet you still felt sad when you watched Mufasa die. There's someone who LOVES the lion king so much that he spends all day watching the lion king. His name is Mr Chalmers and he thinks that trying to explain to mummy and daddy what your feeling of sadness is like, is really really hard. He thinks it's really really hard, because although we know that the grey stuff in your head has something to do with your feeling of sadness, we can't quite figure out why it has anything to do with feeling sad, and how it has anything to do with feeling sad. On the one hand we have your feeling of sadness, and on the other we have a small lump of grey stuff. The small lump of grey stuff doesn't seem to have anything to do with your feeling of sadness, and your feeling of sadness doesn't seem to have anything to do with the small lump of grey stuff.