The role of meaning is central to architectural theory. An important function of the built environment - beyond the quantitative utilitarian concerns - is to make habitable space comprehensible. As Scully writes :
Human beings fashion an environment for themselves, a space to live in, suggested by their patterns of life and constructed around whatever symbols of reality seem important to them. Most of all, that environment and those structures invest the vast indifference of nature with meanings intelligible to, indeed imagined by, mankind.
Before we can design meaningful environments, we must understand how meanings operate. Hesselgren describes three "attributes" of meaning, and three ways in which a meaning may arise from a perception . The attributes of meaning are:
The links from perception to meaning are:
These attributes and perceptual links form a matrix of shades of meaning. The specific values described above rarely occur in isolation: the perceptions that guide us through our environments usually conjure up a cocktail of semantic links and attributes.
The distinction between associative and spontaneous meanings is open to discussion. In Hesselgren's scheme, associative meanings must be learned and may be local to a group or culture, whereas spontaneous meanings are "natural" and universal. But while certain expressions - smiles, frowns, laughter, weeping - may be universal and biologically "wired", it may be that infants must nevertheless learn their meaning. More to our purposes, gravity-related cues to meaning that seem natural and universal on Earth may turn out to be cultural and not applicable to micro-gravity or artificial-gravity environments.
For a perception to carry a meaning, it must be recognizable. Hesselgren  and Prak  stress the importance of gestalts, both in composing the environment and in reading it. A gestalt is a structure, configuration, or pattern of phenomena that constitutes a semantic unit with a meaning that is not derivable from its parts. For example: a square is immediately recognizable as such; its perceived "squareness" does not depend on a rational analysis of discreet edges and angles. In fact, such an analysis often serves to contradict an initial perception: what was thought to be a square may upon closer examination turn out to be a rectangle or rhombus; its corners may be rounded, crossed, or unclosed. Within some small tolerance, a non-square stimulus may give rise to the perception of a "square" gestalt.
An important concept of gestalt psychology is pregnance. A pregnant perception is one that is distinguishable from similar perceptions within a very small tolerance of stimulus. An example of this is the right angle. Small deviations from 90 degrees are readily perceptible as acute or obtuse. Within a tolerance, one "expects" a right angle, and very small deviations from 90 degrees are not perceived at all. Other angles do not possess this quality of pregnance. Without the aid of measurement instruments or side-by-side comparison, angles between, for example, 20 and 30 degrees are perceived as the same acute angle.
As the previous two paragraphs indicate, the cognitive path from stimulus to perception is not a hard-wired, knee-jerk reflex. Conclusions can not be drawn from stimulus to perception, nor vice-versa.
The gestalts are the "words" of the vocabulary of perceptions, from which higher-level meanings - sentences, paragraphs, and stories - are composed. The flood of perceptions that we receive from the local environment create what Norberg-Schulz calls the genius loci - the spirit of place :
Man dwells when he can orient himself within and identify himself with an environment, or, in short, when he experiences the environment as meaningful. Dwelling therefore implies something more than "shelter". It implies that the spaces where life occurs are places, in the true sense of the word ... Architecture means to visualize the genius loci, and the task of the architect is to create meaningful places, whereby he helps man to dwell.
This may explain the continuing public fascination with the torus as a space station form, even when its relationship to rotation and artificial gravity is satirized, misunderstood or ignored. This is evident in posters produced by the International Space University and the Shimizu Institute, as well as sets for movies and television shows such as Star Trek. The torus is a simple form that is perceived whole, even if its rationale is not. In contrast, real space stations such as Mir and Freedom are complex assemblies of forms with configurations that appear arbitrary and meaningless to the untrained eye. To paraphrase Meyers: People "know" what a space station looks like - and it's not "Freedom" .