ABSTRACT
This chapter begins by introducing two key principles by which philosophical theories of visual perception may be distinguished from one another: the Phenomenal Principle and the Common Factor Principle. The Phenomenal Principle states that if I am consciously aware of a property, then a bearer of that property must exist for me to be consciously aware of. The Common Factor Principle states that any indiscriminable perceptual experiences, including veridical perceptions, hallucinations, and illusions, have an underlying mental state in common.
