  In both De Anima and the Parva Naturalia, Aristotle assumes something which may strike some of his modern readers as odd. He takes psychology to be the branch of science which investigates the soul and its properties, but he thinks of the soul as a general principle of life, with the result that Aristotle’s psychology studies all living beings, and not merely those he regards as having minds, human beings. So, in De Anima, he takes it as his task to provide an account of the life activities of plants and animals, along side those of humans (De Anima ii 11, 423a20–6, cf. ii 1, 412a13; cf. De Generatione Animalium ii 3, 736b13; De Partibus Animalium iv 5, 681a12). In comparison with the modern discipline of Psychology, then, Aristotle’s psychology is broad in scope. He even devotes attention to the question of the nature of life itself, a subject which falls outside the purview of psychology in most contemporary contexts. On Aristotle’s approach, psychology studies the soul (psuchê in Greek, or anima in Latin); so it naturally investigates all ensouled or animate beings.