The word ego can refer to a sense of separate I, or the psychological ego, the operating system for our human self.
When I explore ego – in the first meaning – through the six sense fields, I find that it is just a thought arising here now, taken as true.
Attention gets absorbed in the inside of the thought, there is an identification with it, it is anchored on certain sensations which lends it an appearance of substance and reality – and also a location in space, it becomes a fixed view and identity, and with the sense of the thought being right and true, its reversals become wrong and false, so there is a sense of I and an Other.
“Ego” then is as ephemeral and insubstantial as a thought, since that is all it is. But taking a thought as true has very real effects for our human self in the world, as we can explore through for instance The Work.
This is of course a simplified version of it. When we explore, we can always find new layers of complexity and richness of this – quite beautiful – process.
In terms of the layers of thoughts, I find a layer of space, mapping the five sense fields on a sense of space and extent. And I find an identification with a thought, any thought, which is then mapped on sensations appearing in particular locations in space, guided by an image thought of this body which maps sensations, and this creates a sense of a separate I, of center and periphery.