Reflexion (Hegel’s spelling, distinct from “reflection”) is Georg Wilhelm Friedrich Hegel’s term for the movement by which something turns back upon itself, incorporating its own limit or boundary into itself. In the Science of Logic, reflexion is how essence relates to itself through what it has posited — the reflected light returns to the source and changes it.
This concept is referenced by the relationality derivation at step 5 (Reflexion), where the bounded unit folds its boundary back into itself. The unit does not merely have a boundary; through reflexion, the boundary becomes part of what the unit is. The derivation uses the older spelling “reflexion” to mark this specific meaning: self-engagement through the integration of one’s own limit.