There is little doubt that having a theoretic foundation will benefit the field of visualization, including its main subfields. Because there has been a substantial amount of work on taxonomies and conceptual models in the visualization literature and some recent work on theoretic frameworks, such a theoretic foundation is not a foolish or impractical ambition. This article asks, "How can we build a theoretic foundation for visualization collectively as a community?" The authors envision the pathways for four different aspects of a theoretic foundation: taxonomies and ontologies, principles and guidelines, conceptual models and theoretic frameworks, and quantitative laws and theoretic systems.