Geons are the simple 2D or 3D forms such as cylinders, bricks, wedges, cones, circles and rectangles corresponding to the simple parts of an object in Biederman's recognition-by-components theory. The theory proposes that the visual input is matched against structural representations of objects in the brain. These structural representations consist of geons and their relations (e.g., an ice cream cone could be broken down into a sphere located above a cone). Only a modest number of geons (< 40) are assumed.

This is what I was trying to talk about! Basic—indeed innate—shapes “in the brain.” Meaning acts of schematism that create complex imaginary objects that are ready-made, as wholes, due to the fact that they are compelled by innate multi-part algorithms. These actions are simple, but they are determinate and qualitatively specific. Cones are appreciated as a real class or natural kind. Cones and spheres are stable and on the forefront of our attention’s intentionality. I don’t routinely make jabberkunks because, well, the economy of biology, the mechanism of primate space-and-self representation, and pro-survival effects of the latter have conspired to construct me without them. They are not in my innate glossary of “simples I spontaneously like to imagine.”

Why just these? Economy and simplicity (which is fundamental economy). A small number of simples, through combination and rigid deformation, “billions of possible 2- and 3-geon objects can be generated”—and any encountered object stored as algorithmic construction out of them.

Geons—interesting properties

2. Stability or resistance to visual noise: Because the geons are simple, they are readily supported by the Gestalt property of smooth continuation, rendering their identification robust to partial occlusion and degradation by visual noise as, for example, when a cylinder might be viewed behind a bush.

• Amazing! A bushy thing behind a bush could not be picked out by a positing superimposed outline. A chaotic puffy shape with irregular periphery cannot be sketched over the bush that occludes it. But an ice-cream cone (cone + sphere) can. The subject likes to apprehend its own tracings-over physical space when these tracings flow from innate samskaras or vasanas of image-making. We absorb (and retain) best when we construct most easily.