Psychology's first paradigm.

By the end of the nineteenth century, psychology had become a mature scientific discipline unified around a common paradigm. Although the underlying unity of the field was recognized at the time, it has generally been obscured in later historical writings. In this article, the first "mentalist" paradigm of scientific psychology is examined. The mentalists shared a common definition of the field, two accepted modes of observation, and a common conception of the relationship between modes of observation and data thus observed. Rival schools advanced competing articulations of this shared paradigmatic structure.