In the last 25 years, there is no issue in personality psychology which has been as hotly debated as that of consistency. This book introduces scalability as a reasonable and theoretically satisfying conceptualization of consistency. Three empirical studies of scalability are described; their focus is on the role of scalability as a moderator in prediction. This book makes significant inroads in the field of personality measurement, and, by reviewing previous approaches to personality assessment, it provides a sound theoretical basis for the description and mapping of personalities.