This chapter consists of tutorials on three theoretical and methodological issues in visual perception: (a) Foundational questions: the functions of vision, the relationship between percepts and visual neurons, the concept of information, the notion of representation and representational transformation, the relationship between perception and cognition, the concept of modularity and the place of illusions in the development of perceptual theory. (b) Psychophysics: ranging from the simplest threshold theory to the theory of signal detection. We first compare four threshold models: fixed energy threshold—naïve observer, fixed energy threshold—guessing observer, variable energy threshold—guessing observer and variable energy threshold—variable guessing rate. We then review the receiver operating characteristic and ways to distinguish the sensitivity of observers from their response bias. We conclude this section by examining the application of psychophysical methods in a number of contemporary investigations. (c) Environmental regularities and their relation to perceptual regularities: We trace the evolution of the notion of redundancy reduction into the notion of redundancy exploitation leading to the method of covariational analysis. Finally we look in detail at an investigation which deploys covariational analysis to ask how the statistics of contour relationships in natural images may be linked to the characteristics of the processes of contour grouping in visual perception.