Diagrammatic Proofs in Mathematics: (Almost) 20 Years of Research

The objective of this chapter is to introduce some of the views that have been put forward in almost 20 years of research on diagrammatic proofs in the philosophy of mathematical practice. In Sect. 1, some contextual elements will be presented on the reasons why diagrammatic proofs have attracted so much philosophical attention in the past years. In Sect. 2, the “first wave” in the research on diagrammatic proofs based on the analysis of case studies will be described: this is how it started. In Sect. 3, the “second wave,” which is calling for “big pictures” and divides into two different strategies, will be discussed: this is where it is going. In Sect. 4, some conclusions will be drawn.