Regeneration (Lat. regeneratio, Gr. anagennesis and paliggenesia) is a Biblico-dogmatic term closely connected with the ideas of justification, Divine son-ship, and the deification of the soul through grace. Confining ourselves first to the Biblical use of the term, we find regeneration from God used in indissoluble connection with baptism, which St. Paul expressly calls "the laver of regeneration" (Titus, iii, 5). In His discourse with Nicodemus (John, iii, 5), the Savior declares: "Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God." In this passage Christianity from its earliest days has found the proof that baptism may not be repeated, since a repeated regeneration from God is no less a contradiction than repeated physical birth from a mother. The idea of "birth from God" enjoys a special favor in the Joannine theology. Outside the Fourth Gospel (i, 12 sq.; iii, 5), the Apostle uses the term in a variety of ways, treating "birth of God" as synonymous now with the "doing of justice" (I John, ii, 29), now with "faith in Jesus Christ" (I John, v, 1, 4 sq.), and elsewhere deducing from it a certain "sinlessness" of the just (I John, iii, 9; v, 18), which, however, does not necessarily exclude from the state of justification the possibility of sinning (cf. Bellarmine, "De justificatione", III, xv). It is true that in all these passages there is no reference to baptism nor is there any reference to a real "regeneration"; nevertheless, "generation from God", like baptismal "regeneration", must be referred to justification as its cause. Both terms effectually refute the Protestant notion that there is in justification not a true annihilation, but merely a covering up of the sins which still continue (covering-up theory), or that the holiness won is simply the imputation of the external holiness of God or Christ (imputation theory).
The very idea of spiritual palingenesis requires that the justified man receive through the Divine generation a quasi-Divine nature as his "second nature", which cannot be conceived as a state of sin, but only as a state of interior holiness and justice. Thus alone can we explain the statements that the just man is assured "participation in the divine nature" (cf. II Peter, i, 4: divine consortes naturce), becomes "a new creature" (Gal., v, 6; vi, 15), effects which depend on justifying faith working by charity, not on "faith alone" (sola fides). When the Bible elsewhere refers regeneration to the Resurrection of Jesus Christ (I Peter, i, 3) or to "the word of God who liveth and remaineth for ever" (I Peter, i, 23), it indicates two important external factors of justification, which have nothing to do with its formal cause. The latter text shows that the preaching of the Word of God is for the sinner the introductory step towards justification, which is impossible without faith, whereas the former text mentions the meritorious cause of justification, inasmuch as, from the Biblical standpoint, the Resurrection was the final act in the work of redemption (cf. Luke, xxiv, 46 sq.; Rom., iv, 25; vi, 4; II Cor., v, 16). To the above-mentioned ideas of regeneration, generation out of God, participation in the Divine nature, and recreation, a fifth, that of Divine sonship, must be added; this represents the formal effect of justification and is crowned by the personal indwelling of the Holy Ghost in the justified soul (cf. Rom., v, 5; viii, 11; I Cor., iii, 16 sq.; vi, 19, etc.). Since, however, this Divine sonship is expressly described as a mere adoptive sonship (filiatio adoptiva, Greek: uiothesia; cf. Rom., viii, 15 sqq.; Gal., iv, 5), it is evident that "regeneration from God" implies no substantial emerging of the soul from the nature of God as in the case of the eternal generation of the Son of God (Christ), but must be regarded as an analogical and accidental generation from God.
As regards the use of the term in Catholic theology, no connected history of regeneration can be written, as neither Christian antiquity nor medieval Scholasticism worked consistently and regularly to develop this pregnant and fruitful idea. At every period, however, the Sacrament of Baptism was regarded as the specific sacrament of regeneration, a concept that was not extended to the Sacrament of Penance. Irenaeus repeatedly interprets the Pauline term "recreation" as the universal regeneration of mankind through the incarnation of the Son of God in the womb of the Blessed Virgin. The idea of regeneration in the sense of individual justification is most conspicuous in the writings of St. Augustine. With an unrivaled keenness, he evolved the essential distinction between the birth of the Son of God from the substance of the Father and the generation of the soul from God through grace, and brought together into an organic association regeneration, with its kindred ideas, and justification (cf. e.g. "Enarr. in Ps. xlix", n. 2 in "P.L.", XXXVI, 565). Like the Church, St. Augustine associates justification with faith working through charity, and refers its essence to the interior renewal and sanctification of the soul. Thus, St. Augustine is not only the precursor, but also the model of the Scholastics, who worked mainly on the ideas inherited from the great doctor, and contributed essentially to the speculative understanding of the mysterious process of justification. Adhering strictly to the Bible and tradition, the Council of Trent (Sess. VI, capp. iii-iv, in Denzinger-Bannwart, "Enchiridion", 10th ed., 1908, nn. 795-6) regarded regeneration as fundamentally nothing else than another name for the justification acquired through the Sacrament of Baptism. A characteristic view was that of the German Mystics (Eckhart, Tauler, Suso), who prefer to speak of a "birth of God in the soul", meaning thereby the self-annihilation of the soul submerging itself in the Divinity, and the resulting mystical union with God through love.
In Protestant theology, since the time of the Reformation, we meet great differences of opinion, which are of course to be referred to the various conceptions of the nature of justification. In entire accordance with his doctrine of justification by faith alone, Luther identified regeneration with the Divine "bestowal of faith" (donatio fidei), and placed the baptized infant on the same footing as the adult, although he could give no precise explanation as to the way in which the child at its regeneration in baptism could exercise justifying faith (cf. H. Cremer, "Taufe, Wiedergeburt and Kindertaufe", 2nd ed., 1901). Against the shallow and destructive efforts of Rationalism, which made its appearance among the Socinians about the end of the sixteenth century and later received a mighty impulse from English Deism, the German "Enlightenment", and French Encyclopedism, a salutary reaction was introduced by the Pietists during the seventeenth and eighteenth centuries. Leaving far behind the old Protestant view, the Pietists (Spener, A. H. Francke, Zinzendorf) referred regeneration to the personal experience of justification in union with a sincere conversion to a new life, consisting especially in charitable activity. German Pietism, systematically cultivated by the so-called Hernhuter, exercised a beneficial effect on English Methodism, which went about securing and strengthening regeneration in "methodical fashion", and which undoubtedly performed good service in the revival of Christian piety. Especially those sudden conversions—much as are even today striven for and highly prized in Methodist circles, the American revivals and camp meetings, the Salvation Army, and the German Gemeinschaftsbewegung, with all its excrescences and eccentricities—are preferentially given the title of regeneration (cr. E. Wacker, ll Wiedergeburt and Bekehrung", 1893). Since Schleiermacher the variety and confusion of the views concerning the character of regeneration in learned literature have increased rather than diminished; it is indeed almost a case of everyone to his own liking. The greatest favor in Liberal and modern Positive theology is enjoyed by the theory of Albert Ritschl, according to which the two distinct moments of justification and reconciliation hold the same relation to each other as forgiveness and regeneration. As soon as resistance to God is done away with in justification and lack of trust in God—or, in other words, sin—is overcome in the forgiveness of sin, reconciliation with God and regeneration enter into their rights, thus inaugurating a new life of Christian activity which reveals itself in the fulfillment of all the obligations of one's station.
Turning finally to the non-Christian use of the term, we find "regeneration" in common use in many pagan religions. In Persian Mithraism, which spread widely in the West as a religion of the soldiers and officials under the Roman Empire, persons initiated into the mysteries were designated "regenerated" (renatus). While here the word retains its ethico-religious sense, there was a complete change of meaning in religions which taught metempsychosis or the transmigration of souls (Pythagoreans, Druids, Indians), in these the reincarnation of departed souls was termed "regeneration". This usage has not yet entirely disappeared, as it is current among the Theosophists (cf. E. R. Hull, "Theosophy and Christianity", Bombay, 1909; and in connection therewith "Stimmen aus Maria-Laach", 1910, 387 sqq., 479 sqq.). This view should not be confounded with the use dating from Christ Himself, who (Matt., xix, 18) speaks of the resurrection of the dead on the last day as a regeneration (regeneratio).