Moisture in my soul

I was sprawled on the couch while Matthew, my son, was lying on the living room carpet. He was wearing his athletic shoes and as we talked about math (I think), he would move his shoe up and down the wall. The shoe made an interesting squeaky sound. It sounded like there was something trapped inside it. As so often happens, our attention shifted from trig to the possible reasons why a shoe would squeak.

- Maybe, it's moisture, I said.

- Moisture in my sole, he replied.

- Or, moisture in my soul, I added.