Vol 20: Psychoarithmetic
Psychoarithmetic by Maria Montessori provides a view of the working of the human mind through the lens of exercises and study of mathematics (arithmetic, geometry, and algebra and their relationships), as well as applied mathematics in the form of measurement. The intention of the book, to forge a link between psychology and mathematics, is obvious from the title.
The book demands that the reader attend to each and every detail while at the same
time keeping in mind that all the details form part of the whole one is trying to understand. The book also pays homage to the people throughout the ages who have thought and found ways to solve their daily problems of living through mathematics. Yet without developing the mind through exploring mathematics, one cannot utilize these ideas. So the book is intended to be a handbook, for both children and adults, of how to help the mind develop in order to fulfil its potential.