7 - Initial Direction of Higher Development
Spiritual development can take two (diagonal) directions i.e. transcendent and immanent.
So we have heterarchical development that can be defined horizontally in terms of the interior direction or the exterior.
We have hierarchical development that can be defined vertically in terms of the whole direction (holarchy) or the part direction (onarchy).
Finally we have spiritual development - which necessarily entails both heterarchical and hierarchical aspects - that can be defined diagonally in terms of the transcendent and immanent directions.
In early (advanced) spiritual development - as Underhill recognised - one of these directions is likely to dominate (largely determined by personality characteristics). However ultimately for pure union considerable balance must be maintained with respect to both aspects.
So for example the idealistic intellectual type might typically start out on the "higher" stages by following the transcendent direction; by contrast the romantic emotional type might initially follow the immanent direction.
As development gradually becomes more refined both aspects - irrespective of initial preference - are gradually differentiated (and then integrated).