When we look at certain line-drawings, we see three-dimensional objects. The question is why; why not just see two-dimensional images? We theorize that we see objects rather than images because the objects we see are, in a certain mathematical sense, less complex than the images; and that furthermore the particular objects we see will be the least complex of the available alternatives. Experimental data supporting the theory is reported. The work is based on ideas of Solomonoff, Kolmogorov, and the "minimum description length'' concepts of Rissanen.
