Taken in the sense of "the act of teaching" and "the knowledge imparted by teaching", this term is synonymous with CATECHESIS and CATECHISM. Didaskalia, didache, in the Vulgate, doctrina, are often used in the New Testament, especially in the Pastoral Epistles. As we might expect, the Apostle insists upon "doctrine" as one of the most important duties of a bishop (1 Timothy 4:13, 16; 5:17; 2 Timothy 4:2, etc.).
St. Philip the Deacon preached "of the kingdom of God, in the name of Jesus Christ"; and the Samaritans "were baptized, both men and women" (Acts 8). Furthermore, St. Peter and St. John came from Jerusalem and "prayed for them, that they might receive the Holy Ghost"; and doubtless declared to them the doctrine of that Holy Spirit (ibid.).
The work of the Apologists had been to remove prejudices against Christianity, and to set forth its doctrines and practices in such a way as to appeal to the fair-minded pagan. If anyone was moved to embrace the true religion, he was not at once admitted, as in the days of the Apostles. At first he was treated as an inquirer, and only the fundamental doctrines were communicated to him.
https://www.newadvent.org/cathen/05075b.htm
The "Apologeticum adversus Rufinum" dealt with the Origenistic controversies. St. Jerome was involved in one of the most violent episodes of that struggle, which agitated the Church from Origen's lifetime until the Fifth Ecumenical Council (553). The question at issue was to determine if certain doctrines professed by Origen and others taught by certain pagan followers of Origen could be accepted
https://www.newadvent.org/cathen/08341a.htm
It is clear from the diversity of practice at the present day, that there is much uncertainty as to the doctrine concerning confirmation.
These passages suffice to show the doctrine and practice of the Church during the patristic age.
https://www.newadvent.org/cathen/04215b.htm
poisonous doctrines of all the heretics
To maintain such a doctrine
2. Well does one of our own writers say: the philosophers are the patriarchs of the heretics. It is they who have stained with their perverse doctrine the spotlessness of the Church, not knowing that of human weakness it is said: Why is earth and ashes proud?
https://www.newadvent.org/fathers/3001133.htm
There are many places he uses the word doctrine.
https://www.newadvent.org/fathers/3001084.htm
https://www.newadvent.org/fathers/3005.htm
https://www.newadvent.org/fathers/3010.htm
https://www.newadvent.org/fathers/3001053.htm
https://www.newadvent.org/fathers/3001015.htm
https://www.newadvent.org/fathers/30091.htm
https://www.newadvent.org/fathers/27052.htm
https://www.newadvent.org/fathers/2708.htm
"If this is your opinion, or rather since it is your opinion, that all from among the Jews who believe are debtors to do the whole law, you ought, as being a bishop of great fame in the whole world, to publish your doctrine, and labour to persuade all other bishops to agree with you. As for me in my humble cell, along with the monks my fellow-sinners, I do not presume to dogmatize in regard to things of great moment; I only confess frankly that I read the writings of the Fathers, and, complying with universal usage, put down in my commentaries a variety of explanations, that each may adopt from the number given the one which pleases him."
https://www.newadvent.org/fathers/1102075.htm
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