Descartes' definition of humanity as the combination of res extensa and res cogitans has been the representative theory on the debate over body-soul dualism. Since the middle of the 20th century, however, this perspective was challenged by philosophers who upheld the Eliminative Materialism and tended to reduce human mental and sensory activities to the reaction process of the brain. Beginning from the 1980s, with the help of various kinds of sophisticated instruments and the interdisciplinary study of psychology, linguistics, and neuroscience, cognitive science, which describes human nature as a mechanical or physical process without soul/mind, has exerted much impact on western philosophy on the issues of free will, consciousness (Bewusstsein), and mind (Geist), as well as on religion on the issues of soul, faith, and eternity. Are the data from the sophisticated experiments of neuroscience sufficient to give a comprehensive explanation of human activities? Are decisions based on reason and will just a series of mechanical reactions of the nerves in the brain? Does the materialistic view of humanity without soul/mind, without the image of God, and without the original sin nullify the relation between God and human? This paper seeks to answer these questions based upon Karl Rahner's concept of soul/mind (Geist).