textThe computer screen is flat. No matter what is hidden behind - inside of the virtual world - it stays a flat rectangle, two dimensional.
One way of extracting data from reality is using our binocular vision together with the movement of our body in space to obtain information about the spacial dimensions of an object. Seen as a metaphor we use the same method to map the inner function of imaginary/imagined objects. By taking multiple "views" on certain problems, we give shape to them in our mind.
The (computer) screen takes away this posibility by either fixing us to one place or (in the case of virtual reality) by tracking our movements and adjusting the picture we see. Thus it is encouraging our pasivity. The (computer) screen is interactive but it takes over the control of the user. Intractivity is encouraged as long as the user stays in his place and does what he is expected to do.
This concept is then transfered and applied to reality as well. The logic of the computer screen becomes a metaphor for reality.
A shift in perspective gives us a better understanding of the space we are in, of its dimensions and structure, no matter whether real or imaginary. Another aspect is the amount of a shift: Being sensible enough to percieve even slight shifts is the presumption for a swift reaction that may be necessary, because even small shifts can lead to big changes over time.
Thus, a shift is both a tool for mapping reality and for applying changes to it.