Ecological realism and cognitivism are the two major current contenders in the field of cognitive perceptual theory. This thesis examines these theories, and the debate between them. It shows that the debate, as it exists in the literature, is inconclusive, primarily because of problems in the current formulations of the two contending theories. The most obvious difficulties in the two theories are removed, leaving reconstructed versions of both. The debate is then re-examined in the context of the reconstructed theories. It (...) is shown that ecological realism is a special case of cognitivism dealing with the detection of properties of objects in the environment by resonant transduction. It is also shown that neither theory, as it stands, can adequately describe changes in the perceptual abilities of even very simple animals. (shrink)