How we consider anything now is bound to be different than how we would have 1000 years ago. For example, if there is a God, has God changed over time because we have rethought our place in term of Him? If we have souls or minds, have those changed over time because we have retheorized their definition? The answer isn't the easy "no" we would expect.
Perhaps identity has changed over time for precisely that reason: our times have changed, we've altered our environment and hence how we react to our environment, and we've changed how we consider our selves. Descartes' desire to formulate a theory for all time on the mind and God may in fact have been flawed from the beginning.
You can only try to define what you know and can understand without doubt, Descartes believed this, and yet he still desired to theorize the infinite as a fact of all time. In the age of the cyber-, we know longer consider perspective and ideology to be understandable, and hence neither is our understanding of the reality around us. This allows is the possibility to change this reality, and create explicitly the world that people desire to be in.