Visualization as Heuristics: The Use of Maps and Diagrams in 19th Century Epidemiology

Abstract

In this paper, I argue that visualization and the use of figures represent genuine heuristic, knowledge-enhancing tools in scientific inquiry; in fact, visualization shows a distinctive ability in producing genuinely new knowledge by filling theoretical gaps and in solving problems. I show, then, how visualization can be rightfully appraised as a plausible model for the growth of knowledge, gaining a paramount importance when used at the frontier of research. Unrelated here to the notion of intuition, visualization is treated as an ampliative inference and, being obviously related to figures and vision it is also a way of representing knowledge: this double function justifies it as a non-trivial heuristic device, not replaceable by axiomatic-deductive reasoning. A case study is proposed, regarding the London cholera epidemic, spread between August and September 1854. I show how the recourse to dot maps and a “primitive” version of network Voronoi diagrams as instruments of inquiry helped in filling the then existing theoretical gaps consisting in the ignorance of the existence and action of bacteria in disease transmission. Visualization, on the one hand, acted as an effective problem-solving activity, as it permitted the formulation of a successful strategy to stop the spreading of the epidemic; on the other, through the identification of new causes responsible for the spreading of the epidemic, it allowed to surpass the critical theoretical gap at the frontier of epidemiological knowledge.