Apologetics is a field of study concerned with the systematic defence of Christianity. The term "apologetic" is derived from the Greek word apologia (απολογία), which means in defense of (also means "reply" or "answer").
The word "apologetics" is used eight times in the New Testament  The verse most commonly associated as the basis of this:
- " ... but sanctify Christ as Lord in your hearts, always being ready to make a defense to everyone who asks you to give an account for the hope that is in you, yet with gentleness and reverence" (I Peter 3:15)
The Apostles and early Christians preached Christ crucified and resurrected as a veritable fact, and were not in need of any scientific and philosophical structures and dialectical subtleties. And preachers themselves, in the name of Christ, performed miracles through their faith. At first, Christianity was accepted only through faith, and only later did faith itself become an object of reflection. Appearing in a Judeo-pagan world, Christianity, in defending itself from attacks, was forced to disclose the delusions of the pagans and Hebrews. It was necessary to prove to the pagans that the Christian God is the true God; and to the Hebrews that Christ is the Messiah promised by the prophets. In answer to the persecutions of the governing powers, the Christians had to refute defamation and prove that they not only were not injurious to the government, but on the contrary, were very useful, in consequence of the high moral basis of the new teaching. This explains the character of early Christian Apologetics, 
- Sanctify the Lord God in your hearts, and be ready always to give an answer to every man that asks you a reason of the hope that is in you with meekness and fear - Source: I Peter 3:15
In Orthodox theology, term Apologetics is used in regards to defending the true faith against atheists, pagans, Jews and others. This defense, however, is done in a manner that is loving and in order to bear good fruits and should not be polemical or obsessive in manner, which in many cases is considered detrimental to the Apostolic Faith.
The earliest apologists were the Church Fathers. Their apologies cover a wide range of topics including the Divine origin of the Church, Christ's Nature, Scripture, the Theotokos, miracles, Christian social interaction and the function of doctrine.
Orthodox Apologetics, however, has always tried to give an intellectual synthesis of both general and particular apologetic problems, using as a cornerstone the positive method of building the organically whole Christian worldview. The literature of Apologetics is unusually vast, diverse and almost boundless. But, from a strictly Orthodox point of view, a fully complete, whole and deeply absorbing textbook of Apologetics has not yet been prepared.
List of apologetic work
Early Church Fathers (various topics)
The method adopted by the Church to resolve the vital differences of opinion concerning the meaning of the Scriptures was the ecumenical or universal councils, usually called and presided over by the Roman emperor. There were seven councils that were representative of the whole Christian Church and form the key "apologetics" for the Orthodox faith.
- Nicea (325), to settle the Arian dispute
- Constantinople (381), to assert the personality of the Holy Spirit and the humanity of Christ
- Ephesus (431), to emphasize the unity of Christ's personality
- Chalcedon (451), to state the relationship between the two natures of Christ
- Constantinople (553), to deal with the Monophysite dispute
- Constantinople (680), to condemn the Monothelites
- Nicea (787), to deal with problems raised by the image controversy
The next list of important apologetic works relate to the writings by the early Church Fathers. The following list follows a chronological listing of these.
- The Nicene Creed
- "The Fountain of Knowledge," by St. John of Damascus (7th-century).
- Classical apologetics, i.e., proof of the existence of God (including apologists such as Augustine of Hippo and Thomas Aquinas)
- the existence of the Holy Trinity.
- the relationship between the two natures of Christ / the Divine Nature of Christ / Monophysite.
- the humanity of Christ.
- the personality of the Holy Spirit.
- the Virgin Mary being honoured as "Theotokos" or "Panagia".
- the virginity of the Theotokos.
- the Theotokos and the saints as intercessors.
- the place of icons in orthodox worship
- and others ....
Modern Apologies and Apologists
The most recent and most controversial apologetic is that of Ecumenism and will not directly be addressed in this section.
Among the various works on Apologetics written in the 19th and 20th centuries, worthy of note are:
- Ulrici (1806-1884), God and Nature;
- F. Hettinger (1819-1890), Apology of Christianity; and
- J. Ebrard (1818-1888), Apologetics.
- The (GOARCH) website has a list of Apologetics, see GOARCH Modern Apologetics
The Da Vinci Code apologetics
- The Da Vinci Code by Frederica Matthewes-Green (GOARCH)
- The Da Vinci Code:Decoding the Agenda by Rev. Fr. Theodore Stylianopoulos, Th.D. (GOARCH)
- The Da Vinci Code: The X-Files of Ancient Lies by Rev. Frank Marangos, D.Min.,Ed.D. (GOARCH)
Of the Orthodox Russian works in Apologetics, noteworthy are the classic work of:
- the Moscow Metropolitan, Macarius (Bulgakov), An Introduction to Orthodox Theology (6th edition, St. Petersburg, 1897);
- a remarkable two volume textbook for religious academies by Professor N. P. Rozhdestvensky, Christian Apologetics--A Course of Fundamental Theology, (2nd edition, St. Petersburg, 1893); and
- an original investigation of dogmatic theology from an apologetic point of view, by the Professor V. Rev. P. Y. Svetlov, Experiment of Apologetical Exposition of the Orthodox Christian Doctrine, Vol. I and Vol. II (Kiev, 1898).
These remarkable works have not lost their meaning even up to the present time.
Also deserving attention are some other Russian textbooks. For instance, Father Augustine's, A Manual of Fundamental Theology; Professor V. Rev. D. A. Tichomirov's, A Course in Fundamental Theology, St. Petersburg, 1887; Professor V. Rev. Kudryavtsev's, Short Course of Lectures in Orthodox Theology, (2nd edition, Moscow, 1898); Piatnitsky's, Fundamental Theology; Eleonsky's, Brief Report on Fundamental Theology; Petropavlovsky's, In Defence of Christian Faith Against Unbelief and several other works.
- Acts 22:1; 25:16; I Cor. 9:3, II Cor. 7:11, Phil 1:7, II Tim. 4:16 and I Pet 3: 15
- [Note: Excerpt from Orthodox Apologetic Theology by Ivan M. Andreyev, St. Herman of Alaska Brotherhood, 1995, p. 51-65]
- Orthodox Apologetic Theology by Ivan M. Andreyev, St. Herman of Alaska Brotherhood, 1995