When in 374 Ambrose was elected bishop of Milan and baptized, Simplician became his teacher of doctrine. Ambrose used to call Simplician father, as a sign of spiritual relationship. Probably in this period Simplician moved to Milan where he remained.
When in 374 Ambrose was elected bishop of Milan and baptized, Simplician became his spiritual mentor. Ambrose referred to Simplician as father, indicating a close spiritual bond. Possibly during this time, Simplician relocated to Milan where he stayed.