Since antiquity, visual theorists have variously proposed that perception (usually vision) results from unconscious inference. This paper reviews historical and recent theories of unconscious inferences, in order to make explicit their commitments to inferential cognitive processes. In particular, it asks whether the comparison of perception with inference has been intended metaphorically or literally. It then focuses on the literal theories, and assesses their resources for responding to three problems that arise when visual perception is explained as resulting from unconscious inference: the cognitive machinery problem, the sophisticated content problem, and the phenomenal problem.