This chapter explains the commitment to fundamental metaphysical claims that distinguishes various ways of examining the mind in the period between 1300 and 1600. It examines the functions of the soul, whereas the second analyzes them insofar as they are present in a living animal. Psychology as a special field of investigation was developed in the modern period; not until the late nineteenth century did it emerge as an independent discipline that was institutionally recognized as a branch of science. In 1255 Aristotle's writings in natural philosophy officially became part of the curriculum at the University of Paris. The Aristotelian program of a science of the soul was continued and elaborated by many philosophers throughout the late medieval period. From a methodological point of view, it is remarkable that Montaigne does not refrain from presenting a theory about the soul simply because he has given up every philosophical ambition and confines himself to telling anecdotes and talking about personal experiences.