Augustine once said "a person who is a good and true christian should realize that truth belongs to his lord, wherever it is found, gathering and acknowledging it even in literature."

The answer is pagan: “pagan” is the word that should fill the blank line because it’s the word used in that part of Augustine of Hippo’s quote: Augustine once said: “a person who is a good and true Christian should realize that truth belongs to his Lord, wherever it is found, gathering and acknowledging it even in pagan literature, but rejecting superstitious vanities and deploring and avoiding those who ‘though they knew God did not glorify him as God or give thanks but became enfeebled in their own thoughts and plunged their senseless minds into darkness...”.

rivernaysan = anniversary

for some reason there is another anniversary but, that is correct

- r3ktforgood ☕