(Modified 7th June 2013 to include some droodles.)
Some informal experiments are presented whose results help to challenge most theories of vision and proposed mechanisms of vision.
A possible explanatory information-processing architecture is proposed, based on multiple dynamical systems, grown during an individual's life time, most of which are dormant most of the time, but which can be very rapidly activated and instantiated so as to build a multi-ontology interpretation of the currently, and recently, available visual information -- e.g. turning a corner into a busy street in an unfamiliar city. As far as I know, there is no working implementation of such a system, though a very early prototype called Popeye (implemented in Pop2) around 1976 is summarised. Many hard unsolved problems remain, though most of them are ignored by research on vision that makes narrow assumptions about the functions of biological vision.