Hilary is the pre-eminent Latin writer of the 4th century (before Ambrose). Augustine of Hippo called him "the illustrious doctor of the churches", and his works continued to be highly influential in later centuries. Venantius Fortunatus wrote a "vita" of Hilary by 550, but few now consider it reliable. More trustworthy are the notices in Saint Jerome (De vir. illus. 100), Sulpicius Severus ("Chron." ii. 39–45) and in Hilary's own writings. Pope Pius IX formally recognized him as "Universae Ecclesiae Doctor" in 1851.