Contents Include: THE RIVAL DOCTRINES: The problem Monarchic Doctrine, "Intelligence" Oligarchic Doctrine, Formal Faculties Oligarchic Doctrine, Types Anarchic Doctrine, "General level", "Average", or "Sample" Eclectic Doctrine, Two Factors Proposed Explanations of G Universal Mental Competition Hypothesis of Mental Energy THE FUNDAMENTAL FACTS: Proof that G and S Exist Universality of G Amount of G in Different Kinds of Eduction "Special Abilities" and "Group Factors" Goodness and Speed of Response Law of Span, "Attention" Law of Retentivity of Dispositions Law of Inertia, "Perseveration" Law of Fatigue Oscillations in Efficiency Law of Conation, W and C Influence of Age Influence of Heredity and Sex Mind and Body Cardinal Conclusions