The Ophiuchi Hotline is a Sci-Fi classic published in 1977. Varley explores what would happen if: a) Human consciousness and identity could be recorded, and b) They could be downloaded into perfect clones grown in a 6-month time period to age 19. Basically, you could create a physical “backup copy” of yourself every 6 months.
Among other things, murder would become a misdemeanor “crime against property,” with a penalty of “death with automatic reprieve;” versus a felony “crime against humanity,” with a penalty of “permanent death.”
The Ophiuchi Hotline’s protagonist is Lila, and at one point in the narrative there are three of her alive at once. Fascinatingly, each of her multiple identities evolve independently of the others.
Granted, we are not there yet: we cannot yet make clones of ourselves. HOWEVER: in online virtual worlds and social networks, one “meat” avatar can certainly make more than one “online” avatar identity. And in fact, we do this all the time and throughout recorded history. For example: Samurai “art names,” French “noms de plum,” French “noms de guerre,” “le noms en ligne,” and so on.
Part of the drama of several current, online social network tools is whether they insist our online identities must equal our meat identities. People have pushed back hard on this requirement. And I very much identify with them.
Contemporary network theory, including degrees of connection, has acknowledged the fact that the way humans connect powerfully and flexibly to others worldwide in practice is through their multiple affiliations – read, multiple identities.
A friend and mentor of mine years ago told me he identified, in the following prioritized order, with: a) Family, b) Profession, c) Job. If those are not three simultaneous identities, I don’t know what are.