Maria Montessori developed a form of education in the first half of the last century that came to be called by her surname, and research indicates it often has positive outcomes. In the years since its development, tens of thousands of schools worldwide have called their programs Montessori, yet implementations vary widely, leading to confusion about what Montessori edu­cation is. Although there are varied opinions, here we use Dr. Montessori’s books and transcribed lectures to describe the conclusions of her work at her life’s end. We term this final conclusion authentic in the sense of “done in the traditional or original way,” (the primary definition of the adjective in Oxford English Dictionary, 2019). We do not claim that the original is superior to variants; this is an issue for empirical science. Our overarching goal is to provide researchers, policy makers, administrators, teachers, and parents with a benchmark from which to measure and evaluate variations from the education method Dr. Montessori bequeathed at the end of her life. In the ongoing search for alternative educational methods, the time-honored and burgeoning Mon­tessori system is of considerable interest. Dr. Montessori conceptualized the system as a triangle for which the environment, the teacher, and the child formed the legs. Part I of this two-part article examines Dr. Montessori’s view of what constitutes the environment, in terms of its material, tem­poral, and social features. An appendix to Part II summarizes the features. In the ongoing search for alternative educational methods, the time-honored and burgeoning Montessori system is of considerable interest. Dr. Montessori conceptualized the system as a triangle for which the environment, the teacher, and the child formed the legs. Part I of this two-part article examines Dr. Montessori’s view of what constitutes the environment, in terms of its material, temporal, and social features. An appendix to Part II summarizes the features.

Part II of this two-part article continues the discussion of what Maria Montessori viewed to be the important components of her educational system. Because she developed the system over her lifetime, we prioritized later accounts when contradictory accounts were found. Whereas Part I focused on the environment, Part II examines the second and third components of the Montessori trinity: the teacher and the child. This article includes descriptions of Montessori teacher prepara­tion, children’s developmental stages, and the human tendencies on which Montessori education capitalizes. It ends with child outcomes as described by Dr. Montessori and as shown in recent research, and provides an appendix summarizing features of authentic Montessori described in Part I and Part II.