Tertullian was the first to use the word persona for the persons of the Trinity. Those who share the one substance of the Godhead exist in three persona. While substantia refers to what joins and unifies the inner life of the Godhead, persona points to what characterizes and distinguishes it. The Son acknowledges the Father “speaking in his own person under the name of Wisdom.” When God said, “Let us make man in our own image,” He spoke in this way because “He had already His Son close at His side, as a second person, His own Word, and a third person also, the Spirit in the Word’.
The contemporary usage of ‘persona’ implied legal ownership or a ‘mask’ used in theatre. Tertullian probably used the term with reference to these theatrical masks that were worn by Roman and Greek actors to indicate the various parts they were playing within a specific play and to amplify their voices.
Thus Tertullian possibly meant to indicate that the expression “three persons in one substance” meant that the one God played three distinct yet related roles in the great drama of human redemption. However, behind the plurality of roles there was only a single reality. While Tertullian wanted to stress the “personal” character of God, the selection of the term persona - in English “person” - was to become problematic over time. As time went on, person came to be defined as “an individual human being”, thus creating the problem of defining God as “a being”, rather than “Being itself”, the. And, of course, the modern understanding of person is that of a “center of consciousness” has similar implications. The Holy Spirit
Due to his apologetical task, Tertullian is primarily interested in the relationship between the Father and the Son, but he does not leave the Holy Spirit out of the discussion. Jesus promises to pray to the Father so that the Father will send the Holy Spirit who is “another Comforter . . . even the Spirit of Truth,” thus making the Paraclete...