ABSTRACT
Through biological evolution, the most pervasive and enduring constraints governing the external world and our coupling to it are the ones that must have become most deeply incorporated into our innate perceptual machinery. Especially basic are constraints conditioned by such facts as that space is locally Euclidean and three-dimensional and that significant objects, including our own bodies: (1) are bound by two-dimensional surfaces; (2) tend to conserve semirigid shape; (3) have exactly six degrees of freedom of overall position in space; and (4) tend, over time, to move between nearby positions according to a principle of least action. Because our commerce with the world necessarily takes place through the spatially very different medium of a two-dimensional boundary, internal representations need not literally resemble their corresponding external objects and events. The internal and the external must nevertheless approximate a kind of complementary mesh.
