Catholic Scientists: Andresa Casamayor, Mathematician and Writer

Andresa Casamayor (November 30, 1720 - October 23, 1780) was born in Zaragoza, in a wealthy merchant family. At the age of 17 she wrote the first scientific manual written by a woman in Spain, Tyrocinio aritmético. This work is dedicated to the Piarist Fathers of the College of Zaragoza, so it is easy to think that it may have been a Piarist father who educated her. The work is written with a clear didactic intention, to facilitate the instruction to many who cannot achieve it in any other way. It begins by presenting the figures in a simple way, as letters of an alphabet with which we can write all the numbers, as big as we want. Along with the numbers, the book explains our number system, completely positional, which makes it much simpler than Roman numerals and allows us to perform the four arithmetic operations in a systematic way. This way of working is what today can be programmed in a computer and is known as an algorithm. Maria Andresa does not limit herself to presenting the rules of the algorithms in a progressive way in terms of difficulty, but wants her readers to understand why it is done this way; why these algorithms “work”. In addition, he seeks to achieve accuracy and speed in the calculation. Thus, no sooner does he teach a rule than he goes on to apply it to problems in the world of commerce, with coins or weights, preparing his readers for the trades and mercantile calculus.

Father Latassa gives news of a second manuscript by Andresa, “El Parasi solo”, on more advanced arithmetic, with tables for calculating square and cube roots, although it is not known if the manuscript was ever published.

On the other hand, contrary to what was customary in Spain at the time, Maria Andresa did not marry or take the habits of a religious order. Her father died when she was only 18 years old and, shortly after, her friend and collaborator, Fray Pedro Martínez, also died. María Andresa then dedicated herself to her vocation as an educator, working as a teacher of girls in the Public Schools of Zaragoza until her death in 1780.