The question of the reality of the soul and its distinction from the body is among the most important problems of philosophy, for with it is bound up the doctrine of a future life. The soul may be defined as the ultimate internal principle by which we think, feel, and will, and by which our bodies are animated. The term "mind" usually denotes this principle as the subject of our conscious states, while "soul" denotes the source of our vegetative activities as well. If there is life after death, the agent of our vital activities must be capable of an existence separate from the body. The belief in an active principle in some sense distinct from the body is inference from the observed facts of life. The lowest savages arrive at the concept of the soul almost without reflection, certainly without any severe mental effort. The mysteries of birth and death, the lapse of conscious life during sleep, even the most common operations of imagination and memory, which abstract a man from his bodily presence even while awake; all such facts suggest the existence of something besides the visible organism. An existence not entirely defined by the material and to a large extent independent of it, leading a life of its own. In the psychology of the savage, the soul is often represented as actually migrating to and fro during dreams and trances, and after death haunting the neighborhood of its body. Nearly always it is figured as something extremely volatile, a perfume or a breath.
In Greece, the heartland of our ancient philosophers, the first essays of philosophy took a positive and somewhat materialistic direction, inherited from the pre-philosophic age, from Homer and the early Greek religion. In Homer, while the distinction of soul and body is recognized, the soul is hardly conceived as possessing a substantial existence of its own. Severed from the body, it is a mere shadow, incapable of energetic life. Other philosophers described the