Pope St. Soter succeed Pope St. Anicetus as the head of the Holy Catholic Church in 167 and served as the Vicar of Christ until his martyrdom in 175 AD.
We possess a fragment of an interesting letter addressed to him by St. Dionysius of Corinth, who writes: "From the beginning it has been your custom to do good to all the brethren in many ways, and to send alms to many churches in every city, refreshing the poverty of those who sent requests, or giving aid to the brethren in the mines, by the alms which you have had the habit of giving from old, Romans keeping up the traditional custom of the Romans; which your blessed Bishop Soter has not only preserved, but has even increased, by providing the abundance which he has sent to the saints, and by further consoling with blessed words with brethren who came to him, as a loving father his children." "Today, therefore, we have kept the holy Lord's day, on which we have read your letter, which we shall always have to read and be admonished, even as the former letter which was written to us by the ministry of Clement." (Eusebius, Church History IV.24)Besides this, little is known of St. Soter's life.
St. Caius served as the holy pontiff from December 17, 283, until April 22, 296. As the Liberian catalog succinctly states, "He is mentioned in the fourth-century "Depositio Episcoporum" (therefore not as a martyr): X kl maii Caii in Callisti. He was buried in the chapel of the popes in that cemetery. Nothing whatever is known of his life. He lived in the time of peace before the last great persecution."
Like all the Vicars of Christ in the first centuries, St. Soter and St. Caius were constant in uniting their sufferings to those of the Divine Redeemer and "in Him bore much fruit".