On the other hand, if you take something like light, you find it’s very different, so let’s go through some thought experiments. Let’s take two flashlights, aim the two beams of the flashlights at each other and turn them on. What happens? Well, the two beams pass right through each other, nothing at all happens. Now take two water hoses and do the same thing. Now of course you see that the water starts splattering. And although that scattering is mostly electrical, even if you could turn off the electrical charges, then you’d find that the Exclusion Principle would drive the scattering.
So our world’s composed of these two major pieces. And the thing that’s really weird about our world is, like I said, stuff like us seems mostly to be fermions. The other half - energy, light, gravity, what we physicists like to call gauge fields, are all bosons. So why does our universe have this strange dichotomy, where stuff cannot pass through each other, but light and energy can? In fact, wouldn’t the world be sort of more balanced, more symmetrical, or even supersymmetrical, if there were some forms of energy that would scatter each other just the way that stuff, matter, does, and if there were some forms of matter that could pass right through each other just the way energy does?