For Plessner, the living boundary is both a liminal zone that mediates between organism and the outer medium, itself being neither, and yet also an enactively self-defining and enforcing circumference and outer-limit. The organism moves outward in the expansion and assimilation of its liminal zone and moves inward, taking the outer within, re-establishing itself and reasserting its perimeter. The living boundary already introduces a subject-object status that prefigures for Plessner the overcoming of dualisms between inner and outer, interiority and exteriority. The living boundary is an on-going enactment of an exteriority that it defines and yet also reaches into and assimilates and of an interiority that is both sustained and transformed. The motive force of the dynamic living state is this double aspectivity of its existence and the dialectical tension which drives it forward.

Pace Dilthey, Plessner's "Levels" is not about interpreting historical contingencies, nor about the more familiar evolutionary sedimentation of frozen accidents, but rather is about looking to establish transcendental conditions (or categories) of biotic possibility that he refers to as "modals of the organic." As with Hegel he challenges us with a proposed logic of life always mobilized by dialectical tensions, albeit not on the basis of any form of idealism and bereft of a Hollywood ending. For Plessner, that which is both the sine qua non of the living state and that generative 'principle' from which organic modals can be derived is the on-going performance of a self-positioning boundary, and it is highly unlikely that anybody has ever thought as deeply about the implications of what this means.