The document discusses Hans Eysenck's personality theory, which combines both the type and trait approaches. Eysenck proposed that there are three fundamental personality factors - introversion vs extraversion, neuroticism vs emotional stability, and psychoticism vs impulse control. He argued that these traits are determined by heredity and interact to form four basic temperaments: melancholic, choleric, phlegmatic, and sanguine. Eysenck's theory contributed to the study of criminology, education, genetics, psychopathology, and political ideology.