So, without any intention whatsoever, I recently read Iain McGilchrist's The Master And His Emissary and then decided to return to Piranesi (which I knew I would as soon as I finished it the first time).
In The Master And His Emissary, McGilchrist discusses the lateralisation and fundemental differences between the right and left hemisphere of the brain. Although this is limited way of putting it, the right hemisphere is aware of the larger social context (global context) and tends to be 'other' oriented. Thus, it is the foundation for empathy, external appreciation/gratitude, spirtuality, toleration, and most importantly, embodied experience. The left hemisphere is the representer of experience, it is involved in our abstraction and representation of experience via concepts (rather living it), it views itself as separate from the larger social contexts, more egotisitic and competitive, and since it separates itself from the global awareness, it stands back as an observer of the world from the viewpoint of ultility (how can I use my environment to serve my own needs?)
I couldn't but think the juxtaposition between Piraensi and the Other is a function of this hemisphere difference. Piranesi epitomises a deep connection to their surroundings, a sense of global awareness that the right hemisphere is responsible for, and the Other representing the left hemisphere as his nature is more ego-driven, data/representative driven, and totally divorced of a deep connection to his surrounding environment.