Trinity and Virgin and Child from BL Harley 4381, f. 3

Detail of a miniature of the Trinity and the Virgin and Child depicting them flanked by six saints: Peter, Jerome, Gregory, Paul, Augustine, and Ambrose. Image taken from f. 3 of Bible historiale (vol. 1). Written in French, with some Latin for frontispiece.

The concept of the Trinity is a central doctrine of Christianity that refers to the belief in one God who exists as three distinct persons: the Father, the Son (Jesus Christ), and the Holy Spirit. The three persons of the Trinity are equal in power and glory, and yet distinct in their roles and relationships with one another. The Father is the source of all that exists, the Son is the redeemer of humanity, and the Holy Spirit is the comforter and guide of the Church. The doctrine of the Trinity is rooted in the teachings of Jesus and the apostles, as well as in the early Christian Church's reflection on the nature of God and on the experience of God's presence in the world. The Trinity is a mystery that transcends human understanding and cannot be fully grasped by the human mind.

The "BL Harley Manuscript" refers to a collection of medieval manuscripts held in the British Library in London. The Harley Manuscripts are part of the larger collection known as the Harley Collection, which was assembled by Robert Harley (1661–1724) and his son Edward Harley (1689–1741). Robert Harley was a prominent English statesman and bibliophile, and he began amassing a vast collection of books and manuscripts in the late 17th and early 18th centuries.

The Harley Manuscripts are known for their diversity and include a wide range of texts, including historical chronicles, illuminated manuscripts, legal documents, literary works, and scientific treatises. The collection contains over 7,000 manuscripts, and it is considered one of the most important manuscript collections in the British Library.

The Harley Manuscripts are numbered with the prefix "Harley," followed by a specific manuscript number. Each manuscript in the collection has its own unique content and history, and they cover a broad spectrum of topics and time periods. Some of the manuscripts in the collection are beautifully illuminated, with intricate illustrations and decorations.