Letters to Serapion

Four letters addressed to Bishop Serapion of Thmuis defending the full divinity of the Holy Spirit against those who accepted the divinity of the Son but denied it of the Spirit. Athanasius extends the same logic he used against the Arians: if the Spirit sanctifies, divinizes, and gives life, then the Spirit must be fully divine. These letters are among the earliest systematic treatments of the Holy Spirit's divinity in Christian theology.

Letters to Serapion is a central text in the Christian mystical tradition, offering insight into the spiritual life, the nature of divine union, and the transformation of the soul.