A Boundary (n.) knowledge leaves reason neither locked inside the sensible world nor adrift outside it, but attending only to the relation between what lies outside and what lies within.
A Boundary (n.) contains something positive — a surface bounds a body yet is itself a space, a point bounds a line yet is a place — whereas limits contain mere negations.
Boundary (n.) between the sciences must be drawn with care — between a doctrine's home principles and borrowed ones — or no thoroughness in philosophy can be hoped for.
A Boundary (n.) always presupposes a space outside that encloses it; a limit requires nothing of the kind and is a mere negation of completeness.
A Boundary (n.) of reason belongs just as much to experience as to beings of thought — the only place where the ban on transcendence and the command to go beyond can coexist.
A Boundary (n.) can never end the regress: any perception that bounds your series cannot be part of it, since what bounds must differ from what is bounded — so you must go on to it.
A Boundary (n.) differs from a limit as a sphere from a plate: on a flat earth I know only that I can always walk farther; once I know the earth is a sphere, a single degree tells me its whole surface.