Triads and trinity

Was the idea of the Trinity - that One God exists in Three Persons and One Substance - influenced by pre-Christian traditions? It is well known that the New Testament offers no such doctrine, and there is no evidence that Jesus of Nazareth regarded himself as a member of the Trinity. The doctrine was developed during the first four Christian centuries, culminating in the Council of Constantinople in AD 381.
The world of the early Christian centuries in which the Trinity was developed as a tenet of belief included several religious and philosophical systems with similar beliefs. Triads and Trinity examines three possible areas of impact: Judaism, the religion of Egypt, and various Greek traditions. Whereas a pluralistic concept of God was inherited by Judaism, it eventually accepted a firm monotheism. In Egypt the concept of trinity was of ancient origin, but it flourished especially in the second century AD and afterwards, when the mystery cult of Isis reached its acme of popularity in a Graeco-Egyptian framework which found adherents in many countries of the Roman empire. This Graeco-Egyptian religious amalgam exercised a potent influence on early Christian thinkers, particularly in Alexandria.
Using the methods of comparative religion, the distinguished Classicist and Egyptologist J. Gwyn Griffiths has examined the origins of the doctrine of the Trinity and has based his conclusions on a thorough analysis of the original sources in Greek, Latin, Egyptian, Coptic and Hebrew.