 A test for this proposal is how a decomposing synthesis might represent space given that we conceptualize it as infinite. On Rosefeldt’s account, the decomposition into finite parts may involve imaginatively drawing line segments that form a square. We can subsequently extend these lines in the imagination, and we are conscious that we can freely vary the lines so that “however large the finite space that we construct by drawing lines is, this space will always only be phenomenally present to us within the horizon of a still larger unlimited space.” This does not amount to intuiting space as infinite, but rather coming to understand that the space we intuit is infinite by a progressus ad infinitum (A510–11/B538–39), a progression of a series that we understand is never complete (Onof and Schulting 2015). Accordingly, space itself, in this way given as infinite, is an object of intuition for us as the phenomenal horizon of finite regions of space from which we distinguish it in the decomposing synthesis. A parallel account holds for time. This account supplies the meaning, Rosefeldt argues, of Kant’s claim that “a synthesis which does not belong to the senses” is required for “space and time [to be] first given to us as intuitions” (B160–1n).