Sociological systems theory has established a clear distinction between self reference and external reference. Self reference is the ability of an observer to refer to himself in an observation, while external reference means establishing a relation to another identity distinct from the observer. Self reference invokes the notion of self in the world, and especially the handling of self reference and external reference within one observation is considered an important ability enabling the observer to deal with complexity arising from double contingency.
Looking at the concepts of self reference and external reference in the light of the descriptions of observations we worked out in the previous posts, the intrinsic availability of self reference has to be questioned. If we take any one observer as identical with one and only one observation, and view the notion of unity as a construction coming in after the fact of the actual observation, then we would have to place the idea of self reference also in this realm of constructions coming after the fact. If no two observers are the same, then self reference is excluded, at least at this basic level. Here, all references are necessarily external, as no other identity can be the same as the actual observer. Even if the same reference were used, it would necessarily refer to a different observation that happened previously or will happen later.
The consideration of constructions coming after the actual observation has been theorized in the concept of second-order observations. These are defined as observations of observations, and they therefore come with the ability to create new contexts for other observations. Such a context can then be a notion of observer unity, i.e. selfhood. It can just as well include the actualization and reconstruction of another identity, such as a separate person. For a persistent notion of selfhood, it would be essential for both modes of observation to closely relate to each other, thus enabling a coherent construction of self reference. At the same time, any second-order observation is also a first-order observation, in that it also has its own unique observer, who can, at its own basic level, only make external references. These can, however, be constructions of self reference for another, external observation.