While I recovered my equilibrium and composure, I thought to myself: “Well, here I am, sitting on a folding chair, staring through a piece of plate glass at my own brain … But wait,” I said to myself, “shouldn’t I have thought, ‘Here I am, suspended in a bubbling fluid, being stared at by my own eyes’?” I tried to think this latter thought. I tried to project it into the tank, offering it hopefully to my brain, but I failed to carry off the exercise with any conviction. I tried again. “Here am I, Daniel Dennett, suspended in a bubbling fluid, being stared at by my own eyes.” No, it just didn’t work. Most puzzling and confusing. Being a philosopher of firm physicalist conviction, I believed unswervingly that the tokening of my thoughts was occurring somewhere in my brain: yet, when I thought “Here I am,” where the thought occurred to me was here, outside the vat, where I, Dennett, was standing staring at my brain.

— The Mind's I (Penguin Press Science) by Douglas R. Hofstadter, Daniel C. Dennett (Penguin Press Science)