@jj: Thoughts may not be physical in the same way that heat is not physical. Heat occurs in the physical world, but it is our perception of the underlying movement of molecules or infrared photons that is what the average person means by "heat." Just like "purple" or "happy," we are not able really to know how another person perceives "heat."

"I don't know which is worse: ignorance or apathy. And, frankly, I don't care." - Anonymous