Our current paradigm imposes one view on the world. The shift to a new paradigm leads to a radically different way of seeing exactly the same world.
We can only see the world through one paradigm at a time. A paradigm shift is normally one way—from the old to the new. This is because when we see the new paradigm’s world view, we recognise the faults of the old one. The new paradigm then appears obviously better: we are not tempted to shift back.