If I understand you question well. Then I say your mixing between parallel worlds and dimensions. Dimension is a theory (or a thesis I never understood the difference) a fourth dimension would mean a dimension that would employ all previous dimensions, add a characteristic that is relatively new to the previous dimensions (because it is now serving a new function) and of course be of higher order to the previous dimensions.
So the idea is to unveil as many dimensions and by that grasp a better understanding of how universe work.
