Callixtus was first appointed to be a deacon by Pope Zephrynus, who counted him as trustworthy and often sought his counsel in regards to decision-making and theology. Even in his time as deacon, it became evident that Callixtus valued repentance and subsequent forgiveness most highly. As he began to influence Zephrynus toward this end, there were those who viewed this as an unfaithful expression of lawful theology.