First Peter 3:15 declares that Christians must be ready to give a reason for their faith. Christian apologetics are designed to present non-Christians reasons to adopt the Christian faith or to strengthen the belief of current Christians. Also, apologetics within the Christian community provide arguments that support and strengthen the doctrinal and ethical tenets of the Christian faith.

Sociologists of religion, such as Peter Berger and Douglas Cowan, have observed that boundary maintenance of belief occurs when one religious tradition encounters another.

Historically speaking, philosophical apologetics has not been very instrumental in the propagation of the Christian faith or had much interest to many Christians, although it has appealed to Christian intellectuals. The apostle Paul, who was well-educated, said to beware philosophy (Colossians 2:8), though there is evidence that he was acquainted with Greek philosophy himself (Acts 9:29). Evangelical Christian apologist Dr. Norman Geisler composed an essay entitled "Beware of Philosophy: A Warning to Biblical Scholars". Yet some apologists call themselves Christian philosophers, such as Michael Horner. An explanation of this conflict is that Christians view some philosophy as being compatible with Christianity, such as the laws of logic, while other philosophy is not, such as nontheistic philosophy. Also, Francis Schaeffer, a conservative Protestant Christian apologist, argued that Christians needed to be more knowledgeable about philosophical questions, as he taught that only a Judeo-Christian view of man and the world provided satisfactory and consistent answers to the questions of being, knowledge and morals which philosophy addresses.

An influential Catholic apologist was Saint Thomas Aquinas, who presented five arguments for God's existence in the Summa Contra Gentiles. Aquinas's approach, which adapted Aristotelian thought, is known as Thomism, and has dominated both Roman Catholic and Protestant (see Protestantism) approaches.

In the period between 1800 and the mid-1900s, there were a number of Christian apologist/scholars such as:

• William Mitchell Ramsay (1851–1939),
• William Henry Green (1825–1900),
• James Orr (1844–1913),
• Robert Dick Wilson (1856–1930), and
• Oswald T. Allis (1856–1930)

In India the emergence of modern rationalist and atheist beliefs has prompted a counter move from indigenous Christian apologists. The most notable among them is Johnson C. Philip, who authored more than 50 books and 2,500 articles in defense of the Christian faith. He is also the father of the influential Integrated Christian Apologetics.

A common concern in the history of Christianity is that apologetics deny the role of faith and, some argue, that they seem to offer a way to "reason oneself" into the kingdom of heaven, as Blaise Pascal argued. However, many Christians understand the Bible to command the defense of the Christian faith when it says that one should "always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have" (1 Peter 3:15). Some believers assert that a proper view of faith involves not simply accepting that what the Bible says is true, nor only trusting that God exists, but actually trusting in God, citing as an example that Satan's mere knowledge of God is insufficient for his own salvation (James 2:19).

Christian apologetics continues to the current day in various forms. The Roman Catholic G. K. Chesterton, the Anglican C. S. Lewis, the evangelical Norman Geisler, the Lutheran John Warwick Montgomery, and the Presbyterian Francis Schaeffer were among the most prolific Christian apologists in the 20th century.

Among the most widely read Christian apologists writing in English have been Josh McDowell and Lee Strobel. Another modern apologist is Ravi Zacharias, author of The Lotus and the Cross: Jesus Talks with Buddha, which argues for Christian truth over against world religions and other modern movements.

Other leading Christian apologists include:

• Gleason Archer,
• Greg Bahnsen,
• F. F. Bruce,
• Gordon Haddon Clark,
• William Lane Craig,
• Gary Habermas,
• Kenneth Kitchen,
• Bruce Metzger,
• J. P. Moreland,
• R. C. Sproul,
• Merrill Unger,
• Cornelius Van Til, and
• Edwin M. Yamauchi

• historical apologetics,
• legal evidentialist apologetics,
• presuppositional apologetics,
• philosophical apologetics,
• prophetic apologetics,
• doctrinal apologetics,
• biblical apologetics,
• moral apologetics, and
• scientific apologetics.

In the evidentialist tradition, empirical arguments about the supposed life, miracles, death and resurrection of Jesus are presented as probabilistic proofs.

The Catechism of the Catholic Church, following the Thomist tradition of St. Thomas Aquinas and the dogmatic definition of the First Vatican Council, affirms that it is a doctrine of the Roman Catholic Church that God's existence can in fact be rationally demonstrated. Some other Christians in different denominations hold similar views. On this view, a distinction is to be drawn between (1) doctrines that belong essentially to faith and cannot be proved, such as the doctrine of the Trinity or the Incarnation, and (2) doctrines that can be accepted by faith but can also be known by reason; that is, truths revealed by special revelation and by general revelation. The existence of God is said to be one of the latter. As a theological defense of this view, one might cite Paul's claim that pagans were without excuse because "since the creation of the world [God's] invisible nature, namely, his eternal power and deity, has been clearly perceived in the things that have been made" (Rom. 1:20).

The first Protestant textbook of apologetics was written by the Dutch legal scholar Hugo Grotius, On The Truth of the Christian Religion. This work, which remained in print until the late 19th century, defended the historicity of the Gospels and also addressed arguments to Jews and Muslims.

Christian scholar Gary Habermas is recognized as being one of the foremost defenders of the historicity of Jesus Christ's resurrection.

Various arguments have been put forth by legal scholars such as Simon Greenleaf and John Warwick Montgomery and others claiming that Western legal standards argue for the historicity of the resurrection of Christ. In addition, legal authorities' opinions regarding the resurrection of Christ are appealed to.

Christian scholar Edwin M. Yamauchi, James Patrick Holding and others argue against the pagan myth hypothesis for the origin of Christianity. In addition, Roman historian A.N. Sherwin-White, is often quoted by Christian apologists in regards to Christianity not being formed though myth.

Sherwin-White stated:

"The agnostic type of form-criticism would be much more credible if the compilation of the Gospels were much later in time.. Herodotus enables us to test the tempo of myth-making, [showing that] even two generations are too short a span to allow the mythical tendency to prevail over the hard historic core." (A.N. Sherwin-White, Roman Society and Roman Law in the New Testament, (Oxford: Clarendon Press), 1963. pp. 189-190).

In addition, Sherwin-White stated:

"For the New Testament of Acts, the confirmation of historicity is overwhelming. Any attempt to reject its basic historicity, even in matters of detail, must now appear absurd. Roman historians have long taken it for granted. {A. N. Sherwin-White, Roman Society and Roman Law in the New Testament (Oxford: Clarendon Press, 1963), p. 189).

Bible prophecy is used as an argument for Christianity. It is argued that only God knows the future and the Bible prophecy of a compelling nature has been fulfilled. Peter Stoner is often cited by Protestant apologetic works in regards to Bible prophecy.

Biblical apologetics include issues concerned with the authorship and date of biblical books, biblical canon, and biblical inerrancy. In addition, Christian apologists defend and comment on various books of the Bible. Some scholars who have engaged in the defense of biblical inerrancy include:

• Robert Dick Wilson,
• Gleason Archer,
• Dr. Norman Geisler, and
• R. C. Sproul.

• John Wenham,
• Norman Geisler,
• Kenneth Kitchen, and
• Bryant G. Wood.

Philosophical apologetics concerns itself primarily with arguments for the existence of God, although they do not exclusively dwell on this area.

These arguments can be grouped into several categories:

• Cosmological argument - Argues that the existence of the universe demonstrates that God exists. Various ancillary arguments from science are often offered to support the cosmological argument.
• Kalam cosmological argument is a version of the Cosmological argument derived from the Islamic Kalam form of dialectical argument. It attempts to prove the existence of God by appealing to the principle of universal cause. Similar arguments are found in the theologies of Judaism (for example, in the work of Maimonides) and Christianity (for example in Thomas Aquinas), where it is known as the "uncaused cause" or "first cause" argument.
• Teleological argument (argument from design) - Argues that there is an intricate design in the world around us, and a design requires a designer. Cicero, William Paley, and Michael J. Behe employed this argument as well as others.
• Ontological argument - Argues that the very concept of God demands that there is an actual existent God.
• Moral Argument - Argues that if there are any real morals, then there must be an absolute from which they are derived.
• Transcendental Argument - Argues that all our abilities to think and reason require the existence of God.
• Presuppositional Arguments - Arguments that show basic beliefs of theists and nontheists require God as a necessary precondition .

Presuppositional apologetics
Another apologetical school of thought, a sort of synthesis of various existing Dutch and American Reformed thinkers (such as, Abraham Kuyper, Benjamin Warfield, Herman Dooyeweerd), emerged in the late 1920's. This school was instituted by Cornelius Van Til, and came to be popularly called Presuppositional apologetics (though Van Til himself felt "Transcendental" would be a more accurate title). The main distinction between this approach and the more classical evidentialist approach mentioned above is that the Presuppositionalist denies any common ground between the believer and the non-believer, except that which the non-believer denies, namely, the assumption of the truth of the theistic worldview. In other words, Presuppositionalists don't believe that the existence of God can be proven by appeal to raw, uninterpreted (or, "brute") facts, which have the same (theoretical) meaning to people with fundamentally different worldviews, because they deny that such a condition is even possible. They claim that the only possible proof for the existence of God is that the very same belief is the necessary condition to the intelligibility of all other human experience and action. In other words, they attempt to prove the existence of God by means of appeal to the alleged transcendental necessity of the belief -- indirectly (by appeal to the allegedly unavowed presuppositions of the non-believer's worldview) rather than directly (by appeal to some form of common factuality). In practice this school utilizes what have come to be known as Transcendental Arguments for the Existence of God. In these arguments they claim to demonstrate that all human experience and action (even the condition of unbelief, itself) is a proof for the existence of God, because God's existence is the necessary condition of their intelligibility.

Another position that is also sometimes called Presuppositional apologetics, but should not be confused with the Van Tillian variety discussed above, is the one of Gordon Clark and his disciples. Clarkians hold that, if Christian theology is true, then God's existence can never be demonstrated, either by empirical means or by philosophical argument. The most extreme example of this position is called fideism, which holds that faith is simply the will to believe, and argues that if God's existence were rationally demonstrable, faith in His existence would become superfluous. In The Justification of Knowledge, the Calvinist theologian Robert L. Reymond argues that believers should not attempt to prove the existence of God. Since he believes all such proofs are fundamentally unsound, believers should not place their confidence in them, much less resort to them in discussions with non-believers; rather, they should accept the content of revelation by faith. Reymond's position is similar to that of his mentor, Clark, which holds that all worldviews are based on certain unprovable first premises (or, axioms), and therefore are ultimately unprovable. The Christian theist therefore must simply choose to start with Christianity rather than anything else, by an unreasoned "leap of faith".

Ontological argument

Doctrinal Christian apologetics

Moral Christian apologetics

In the first centuries AD, a number of Christian writers undertook the task of proving that Christianity was beneficial for The Roman Empire and for humanity as a whole. Also, they wrote to defend their faith against attacks made by other people or to properly explain their faith. Aristides and Quadratus of Athens, writing in the early second century, were two of the first Christians to write apologetics treatises. Other second-century apologetic writings of note included the First Apology and Second Apology of Justin Martyr and the Epistle to Diognetus , a response to the accusation that Christians were a danger to Rome.

About a century after Constantine's conversion to Christianity, the Roman Empire began falling to invaders from northern Europe. Some Christian writers sought to explain the decline of Roman culture and power by systematically downplaying the achievements of classical antiquity while emphasizing the persecution of Christians and the positive role of Christianity in society. Paulus Orosius wrote the first book advancing this perspective (History Against the Pagans), though the far more learned and influential work of this type was The City of God by Saint Augustine of Hippo (426).

Several of the early Christian apologists developed arguments from fulfilled prophecy and gospel miracles as proofs of Christ's divinity. Eusebius of Caesarea in his Demonstration of the Gospel attempted to prove the truth of Christianity by fulfilled prophecies from the Old Testament, and by rebutting arguments that the Apostles had made up the story of Christ's resurrection.

Scientific Christian apologetics

Various arguments are put forth from Christians arguing that the GodBible is responsible for the existence of the universe as we find it today (Creationism). Topics such as the creation of matter and energy, the existence of scientific laws, the origin of life, and the origin of various types of animals and plants on the earth are focused on.

Criticisms of Christian apologetics

Lastly, there is a difference between assertiveness and aggressiveness. Most non-Christians and Christians agree that aggressive and/or coercive methods should not be employed by Christians and that Christians should make every effort to be kind and gracious towards those who hold differing views. This verse is often cited:

"And the Lord's servant must not quarrel; instead, he must be kind to everyone, able to teach, not resentful. Those who oppose him he must gently instruct, in the hope that God will grant them repentance leading them to a knowledge of the truth." (2 Timothy 2:24)

Christian apologetics today

Among the most widely read Christian apologists writing in English have been Josh McDowell and Lee Strobel. Another modern apologist is Ravi Zacharias, author of The Lotus and the Cross: Jesus Talks with Buddha, which argues for Christian truth over against world religions and other modern movements. Other leading Christian apologists include: Gary Habermas, F. F. Bruce, William Lane Craig, Kenneth Kitchen, Bruce Metzger, Gleason Leonard Archer, R. C. Sproul, Merrill Unger, Greg Bahnsen, Cornelius Van Til, Gordon Haddon Clark, and J.P. Moreland.

Some Christian apologists include:

• Jimmy Akin
• Gleason Archer
• Greg Bahnsen
• Francis J. Beckwith
• Craig L. Blomberg
• Edward John Carnell
• Gordon Haddon Clark
• Mal Couch
• William Lane Craig
• William Dembski
• John Frame
• Norman Geisler
• Michael Green
• Douglas R. Groothuis
• Gary Habermas
• Carl F. H. Henry
• Karl Keating
• Scott Hahn
• Kimberly Hahn
• Hank Hanegraaff
Carl F. H. Henry
• Dietrich von Hildebrand
• Karl Keating
• D. James Kennedy
• Greg Koukl
• Peter Kreeft
• C. S. Lewis (Clive Staples Lewis)
• Walter Ralston Martin
• John Macarthur
• Patrick Madrid
• Alister McGrath
• Henry M. Morris
• J.P. Moreland
• Clark Pinnock
• R. C. Sproul
• Robert Sungenis
• Bernard Ramm
• Cornelius Van Til
• Dietrich von Hildebrand
• Jonathan Sarfati
• Ken Ham
• Carl Wieland
• Nicholas Wolterstorff

Apologetics in non-Christian religions

One of the earliest Buddhist apologetic texts is The Questions of King Milinda, which deals with ethical and intellectual problems. In the British colonial era, Buddhists in Ceylon (now Sri Lanka) wrote tracts that challenged and rejected Christianity. In the mid-nineteenth century, encounters between Buddhists and Christians in Japan prompted the formation of a Buddhist Propagation Society. In recent times A. L. De Silva, an Australian convert to Buddhism, has written a text designed to refute the arguments of Christian evangelists. At a sophisticated academic level, Gunapala Dharmasiri has challenged the Christian concept of God from a Theravadan Buddhist perspective.

Apologists for Islam have defended the Qur'an using rationalist and empiricist arguments, and using cosmological arguments to "prove" God's existence. Muslim apologists have also challenged both Jewish and Christian beliefs. The late South African, Ahmed Deedat, was a prolific popular writer who debated Christian evangelists by arguing over discrepancies in the Bible, and claiming the Gospel of Barnabas is the only authentic record of Jesus' life.

Hindu apologetics designed to counter Christian missions developed in the British colonial era. Richard Fox Young has collated examples of these early apologetic tracts.

In a famous speech in 1805, Seneca chief Red Jacket was an apologist for Native American religion, as opposed to Christianity.

see also:
Jewish eschatology
Josh McDowell's Apologetics Resource Center,
Timeline of Christianity