Literally the ‘science of God’. Among the Greek Fathers the word came to denote either the doctrine of the Trinity (i.e. of God's Being as opposed to His dealings with the created order) or prayer (as it is only in prayer that God is truly known). In the W. it came to mean the science of the Divinely revealed religious truths. Its theme is the Being and Nature of God and His creatures, and the whole complex of the Divine dispensation from the Fall of Adam to the Redemption through Christ and its mediation to people by His Church; it includes the so-called natural truths of God, which are accessible to mere reason. Its purpose is to investigate the contents of belief by means of reason enlightened by faith and the promotion of its deeper understanding.