It is rather a deduction from and an interpretation of the thought and the language of the New Testament."[52] The New Catholic Encyclopedia states : "The doctrine of the Holy Trinity is not taught [explicitly] in the [Old Testament]", "The formulation 'one God in three Persons' was not solidly established [by a council] ... prior to the end of the 4th century."[53] Similarly, Encyclopedia Encarta states: "The doctrine is not taught explicitly in the New Testament, where the word God almost invariably refers to the Father. ... The term trinitas was first used in the 2nd century, by the Latin theologian Tertullian, but the concept was developed in the course of the debates on the nature of Christ ... In the 4th century, the doctrine was finally formulated".[54] Encyclopædia Britannica says: "Neither the word Trinity nor the explicit doctrine appears in the New Testament, nor did Jesus and his followers intend to contradict the Shema in the Old Testament: "Hear, O Israel: The Lord our God is one Lord" (Deuteronomy 6:4). ...