Apologetics (a word derived from Gr. apo, 'from,' and logos, 'speech'—something spoken to ward off an attack) technically connotes that branch of theology which is concerned with the defence of Christianity. It is not to be confounded with polemies, which is occupied with the defence of the peculiar doctrines of parties within the Christian pale. A work has come down to us, written by Xenophon, entitled the Apology of Socrates, and another, with the same title, by Plato. From these the Christian fathers adopted the term. As a distinct branch of theological science, apologetics cannot be dated further back than the 18th century. Isolated apologies, however, appeared from time to time, from the days of Justin Martyr (d. 168) downwards. Thus, as against the Ebionites and Gnostics (q.v.), were written Justin's two Apologies and his Dialogues. Against Celsus (q.v.), a philosopher of the 2d century, who, among other things, ascribed the paternity of Christ to a Roman soldier, Origen (q.v.) wrote. Porphyry, a philosopher of the 3d century, strove to reduce Christ to the level of the ancient philosophers of Greece. Against him, Eusebius of Cæsarea, Theodoret, and Augustine (q.v.) wrote. In the 4th century, the Emperor Julian, known as the Apostate, endeavoured to rehabilitate paganism in the place of Christianity. He was combatted by Cyril of Alexandria, who wrote ten books against him. In medieval times, various apologetic works were written by Anselm of Canterbury (d. 1109); by Abelard (d. 1142); and by Thomas Aquinas, the doctor angelicus (d. 1274).
As a distinct branch of systematic theology, apologetics is treated under two great heads—viz. Natural Theology and Revealed Theology. Proceeding upon the former of these lines, and confining himself entirely to the light of nature, the apologist endeavours to prove the existence of God, and the possibility of knowing Him. He then goes on to prove the existence of the human soul, and the doctrine of a future life. In working out the theistic argument, two methods are adopted—viz. the ontological, or a priori, which reasons from cause to effect, from self-evident principles prior, in logical order, to experience, to their application; and the teleological, or a posteriori, which, reversing the former process, reasons from effect to cause, from observed facts to a general principle. The a priori argument has been variously set forth by Anselm, Descartes, Dr S. Clarke, Cousin, Ferrier, and Gillespie; and the a posteriori by a host of writers, among whom may be named Paley, Natural Theology; Chalmers, Kidd, Bell, Buckland, &c. in the Bridge-water Treatises; Flint, Baird Lectures; Conder, The Basis of Faith; Janet, Final Causes; and various Bampton lecturers. It is now generally admitted that these two arguments cannot be absolutely separated—something from experience enters into the a priori argument, and, vice versa, an a priori element enters into experience. When, however, we gather into a focus all the evidence furnished by causation, order, and intuition, the apologist maintains that the argument for theism is simply irrefragable. To the objection that though the existence of God may be thus proved, we cannot, owing to the relativity of our knowledge, in any true sense know Him, the apologist replies that He may be as truly known as any other object, by the contemplation of His attributes as disclosed in His works. The theist does not profess to comprehend the Infinite One; all that he asserts is that he is capable of truly apprehending Him. His knowledge, as far as it goes, is true knowledge.
The argument for the existence of the soul, and for a future state, is based upon physiology, psychology, and moral government. It is maintained that the closest scrutiny of man's physical organisation leads up to the conclusion that his loftiest endowments—self-consciousness, reason, and conscience—must inhere in a substance other than material. When, again, the data which consciousness furnishes are duly weighed, it is asserted that man's intellectual capacities, his intuitions, and his aspirations clearly intimate that his true environment is the infinite and the eternal. Special stress is laid upon the testimony of conscience.
Man's sense of moral responsibility, it is argued, shows that his present state of existence is manifestly one of discipline and probation. Such a state would, however, be utterly meaningless if, at death, he were to drop into non-existence. See, as against materialism, Lotze, Microcosmus (Eng. trans. 1886); and on the argument from moral government, Kant, Metaphysics of Ethics; see also Pascal, Thoughts; Butler, The Analogy of Religion; and the various writers on natural theology. Of works in which assaults on religion from the side of science are met by arguments from the physical sciences, we may mention Sir J. W. Dawson's Origin of the World (1877); and Professor Henry Drummond's Natural Law in the Spiritual World (1883; 67th thousand, 1887).
In defence of revealed theology, the apologist has been called upon to deal with a wide range of subjects. Since Lessing (q.v.) published the 'Wolfenbüttel Fragments' (now generally ascribed to H. S. Reimarus of Hamburg, who died 1768), that destructive criticism came into vogue which has found such advocates as Strauss and Renan, Kuenen and Wellhausen. Kant's famous Critique of Pure Reason, which denies to pure reason the power of making any certain statements concerning what is divine, gave an impetus to the rationalistic tendencies of the Deists (q.v.), the result of which is seen in modern agnosticism and positivism. Under these combined influences, the supernatural has come to be either denied, or ignored as unverifiable. The Bible, in particular, has been subjected to the severest criticism, with a view to the complete undermining of its authority as a witness for God and for a future life. Apologetics has therefore for its task in this field, to defend the canonicity, and to prove the inspiration and consequent trustworthiness of Sacred Scripture. On these topics, see Westcott, History of the Canon of the New Testament; Charteris, Canonicity; Lee, The Inspiration of Holy Scripture; and Ladd, The Doctrine of Sacred Scripture. There is a tendency in some quarters at present to distinguish the biblical writings into canonical and deutero-canonical (see Ladd, ut supra). As regards inspiration, the verbal theory is abandoned by most. Evangelical writers, however, still advocate a theory of plenary inspiration; but the theory, as held by them, does not usually exclude the possibility of 'circumstantial errors' occurring in Scripture (cf. Briggs, Biblical Study, p. 242). They also distinguish between inspiration and revelation; the current phrase being that the Bible is the record of divine revelation.
Modern apologists, however, do not place these topics in the foreground. Their main concern is to establish the moral perfection of the Christ of the gospels, and then the substantial historical character of the evangelical records. If the sinlessness of Christ is conceded, they maintain, with Origen, that 'He is the miracle of the world'—i.e. He is a moral miracle. In connection with the appearing of such a Being, they say that it is in the highest degree reasonable to look for manifestations of the supernatural in the physical sphere. The one physical miracle on which they are prepared to stake everything is the resurrection. In proof of this event, they push their historical investigations backwards, step by step, through the writings of the early fathers, and specially through the four epistles which the most adverse criticism ascribes to the apostle Paul, until they arrive at within twenty-seven years of the crucifixion. They are then in a position to show that the moral portrayal of Christ which appears in the canonical gospels was at that date extant, and that, moreover, Christian communities founded upon faith in the resurrection of Christ were to be met with from Jerusalem to
Rome. That a 'myth' could have established itself in so short a period, they maintain, is incredible; and as to a hallucination, such as the theory of 'visions' demands, having taken possession of such a multitude of otherwise rational and estimable people—this they regard as palpably absurd. If, then, the moral perfection of Christ and his resurrection are conceded, all is conceded. He was what he claimed to be—the Son of God. On the modern statement of the argument, see Liddon, The Divinity of Jesus Christ (1867); Bruce, The Miraculous Element in the Gospels; and specially Row, A Manual of Christian Evidences (1887). The apologetic works of Luthardt, Christlieb, and Godet are held in high estimation. See INSPIRATION, MIRACLES.