We begin with the Greeks. In several dialogues, notably the Phaedrus, Timeaus, and Republic, Plato divided life into three parts: vegetable life, animal life, and rational life. All living creatures possessed the first in the form of nutrition and reproduction, animals were additionally capable of sensation and locomotion, and humans also had rational souls. Plato’s subsequent influence in Christian theology may be apparent in spirit if not in detail. In Christian theology, human life was not only rational, but also involved an eternal, spiritual soul and an internal, conscious life.