Rather than worrying about which is physical or mental, internal or external Buddha's simile of The Chariot also points out that no matter where one looks, no matter which aspect of our delusional self is examined there is no self, no soul, no ego, no essence, no me, no my, no mine to be found. Examining the totality, we find that the "concept" or "construction" is empty of any self.
By examining carefully each component from the complete assemblage to the last sliver of wood, leather, lubricants and greases, metals, or jewels none of these components can accurately be labeled "self". Each, therefore, may correctly be categorized as "not self".
Therefore, from two totally different approaches, from two distinct directions of logical approach we have Buddha's instruction as to the emptiness of all constructions, physical/mental, internal/external, each thorough and inclusive of the least sub-atomic and energetic particle to the totalities of the multiverse:
1. There is no self
to be found anywhere.
2. Each and every component, every part, every sub-division is not self
.....therefore stop wasting our time looking for such, nor arguing or debating regarding such nonsensical concepts.
resources for further study: http://what-buddha-said.net/drops/II/In ... cation.htm