While there have been significant developments in the technical aspects of assessing mental functioning, there is still much to be debated about the motivations and meanings of measuring the mind. How can mental faculties be objectified and what influence does subjectivity have on the object being measured and the mind measuring it? What are the consequences of quantifying complex and interdependent functions and scaling these measurements for psychometric instruments?The contributors of this edited volume explore these questions by adopting a historical and epistemological approach to consider how psychometric assessment was born and developed within the affirmation of psychology as an empirical science. Chapters explore the birth of the scientific approach, as well as different assessment methods of cognitive abilities and personality traits, and the development of new technologies that support psychological evaluation and its applications in educational and rehabilitative fields.This book is of interest to researchers of human behavior as well as practicing psychologists and psychiatrists who want to deepen their understanding of the historical and epistemological roots of psychological assessment.