Template:Individual-TLP-paragraph-en-5.5423
5.5423 To perceive a complex means to perceive that its constituents are combined in such and such a way.
This perhaps explains that the figure

can be seen in two ways as a cube; and all similar phenomena. For we really see two different facts.
(If I fix my eyes first on the corners a and only glance at b, a appears in front and b behind, and vice versa.)