Visualization is a ubiquitous technology, just like telecommunication. However, unlike a telephone system, humans play an integral part inside the "box" of visualization. This poses a significant challenge in establishing a theory of visualization. Visualization is a ubiquitous technology, just like telecommunication. However, unlike a telephone system, humans play an integral part inside the "box" of visualization. This poses a significant challenge in establishing a theory of visualization. While information theory, which underpins tele- and data communication, has shown to be applicable in many aspects of visualization, it becomes inadequate when we consider various phenomena of perception, cognition, emotion and interaction in visualization. While it is a piece of computer-assisted technology, it cannot distance itself from fundamental questions (e.g., truth, data, information, and knowledge), some of which have been explored by philosophers for thousands of years. We are inspired to address this challenge by building on existing concepts and discoveries in disciplines such as communication, psychology and philosophy.