143One example is the wall effect created by a row of columns in
a way consistent with the principle that is termed the ‘law of
proximity, similarity or continuity’. In some instances, a pair
of columns suffices to generate this effect, as at the Piazzetta
in Venice. The ‘law of closure’ explains why our perception
completes partial spatial demarcations at isolated points as
closed spatial figures. It is why the arrangement of four trees
into a square, or small facade segments or corners of houses
are perceived as a fully defined, squared-off plaza (> closure,
square and street). Conversely, a spatial form is closed only
when elements are available that are amenable to perception
as a figure, i.e. when a sequence of elements or a corridor is
closed by an end wall, visual target, or terminating link, so
that it does not appear extensible at will. According to the
‘law of Prägnanz’ and of ‘simple gestalt’, the spatial inter-
pretation of a linear structure as a figure occurs when it is
simplified in perception. The ‘law of the inner side’ explains
that the > concavity of a form endows a space with gestalt,
and a > convexity endows a body with gestalt. In a public
square, the two factors may compete. As long as a facade fits
itself into the concave contour of the square, it reinforces the
spatial figure. When, on the other hand, the convex body of a
building becomes recognizable, it tends to project out of the
concave contour of the square as a positive figure. According
to the ‘law of symmetry’, when symmetrical and asymmetrical
shapes alternate within a visual field, the symmetrical ones
are more readily endowed with figural properties – a princi-
ple that makes > symmetry in architecture a rigorous tool for
generating order.
The power with which gestalts assert themselves in rela-
tion to a stimulus field allows us to work in architecture with
suggestion. The contours of buildings and spatial delimita-
tions need not be fully materialized; in many instances, edges,
corners or fragments of surfaces suffice in order to render a
constructive configuration recognizable. Even irregularities
are rectified via the ordering power of perceptual principles,