For examples of these interchanges of meaning, we may notice that the Synod of Antioch (a.d. 269), in the Epistle addressed to Paul of Samosata before his deposition, speaking of the unity of Christ’s Person, says that “He is one and the same in His οὐσίᾳ Routh, Rel. Sacr., III. p. 299..”  On this passage Routh remarks that “The words οὐσία and φύσις are sometimes employed by the ancients for a personal subsistence (persona subsistente), as is plainly testified by Photius.”