Nathalie Quintane--from Shoes, p.8

As long as my heels are part of my brain, nerve endings, throughout the body, connect the former directly to the latter: my heel is in my head, and vice-versa. Now, the heel of my shoe, which extends from that of my foot, reinforcing and protecting it, also resides in my brain.

The shoe is not a "second" foot, but--and I notice this during a long walk, when overcome by a sensation that I cannot remove my shoes without also removing my feet--is the foot, and as such, hails from the brain.