Law of Continuity
The gestalt principle that the eye follows a line or curve and continues along it even where it is interrupted.
In depth
Continuity is what makes leading lines work, and it operates across gaps: a line broken by an obstruction is still read as continuing behind it. It also explains a common compositional failure, where a background line running behind a subject appears to pass straight through them.
Examples in practice
A horizon passing behind a standing figure is read as continuous, so a misaligned join on either side looks wrong.