Despite the fact that to date Visual Literacy (VL) scholars have not arrived at a general consensus for a theoretical organization of the VL field, important conceptual investigations have emerged over the past four decades. In this paper we discuss and synthesize those studies. We then present a first attempt toward a cohesive theory of VL. The main components of the proposed VL theory are Visual Perception, Visual Language (ViL), Visual Learning, Visual Thinking, and Visual Communication. Here we focus on discussing ViL and its constituent parts: 1) ViL exists; 2) ViL is holistic; 3) ViL must be learned; 4) ViL may improve learning; 5) ViL is not universal; 6) ViL often needs verbal support. (Contains 2 figures.)