ABSTRACT
The book closes by returning to questions raised in the Introduction, about the nature and apparent truth of mathematics. Answering those questions turns Platonism on its head. Mathematics does not come from the heavens but, rather, is something that humans construct and project out into the world. But then another question remains: If mathematics is a product of human psychology, why is it so effective in building scientific models and making predictions beyond human experience? For example, if ellipses arise from the coordination of mental actions, why do they fit the paths of planets so well? The chapter addresses epistemological questions while summarizing seven themes from prior chapters: projecting mathematical structures into the world, reversible and composable mental actions, the unity of space and number, preserving and transforming units, algebraic extension, how math builds on itself, and equity in action. This concluding chapter relies on prior chapters to summarize the nature of mathematics and mathematical development.
