Organized as a bibliographic essay, this paper examines the many sources available for developing a theory of visual literacy. Several definitions are offered in order to clarify the meaning of the term "visual literacy" so that meaningful research can be conducted on the topic. Based on the review of resources, three recommendations are offered so that visual literacy research and practice may have some philosophical direction and justification: (1) reexamine the older sources suggested by John L. Debes (the "father" of visual literacy) to see if there is any justifiable basis for theory development in visual literacy; (2) review some of the newer sources suggested in this paper that relate to mental imagery, dual coding, mnemonics, and visualization and make some philosophical connections between these newer sources and the older ones in order to develop a substantive theory that is convincing; and (3) design future empirical research that stresses the visual thinking component of the definition advocated in this paper. An alphabetical listing of the references and resources is attached. (RL)