The monk who relinquishes his status after solemn profession and adoption is to be regarded as guilty of sacrilege, and the faithful are warned against all intercourse with him, with a reference to 2 Thess. iii. 14. With this may be compared the uncompromising denunciation in Letter cclxxxviii., and what is said in the first of the three Tractatus Prævii.  It has been represented that St. Basil introduced the practice of irrevocable vows.  cf. Dr. Travers Smith, St. Basil, p. 223.  De Broglie, L’Eglise et l’empire, v. 180:  “Avant lui, c’était, aux yeux de beaucoup de ceux même qui s’y destinaient, une vocation libre, affaire de goût et de zèle, pouvant être dilaissée à volonté, comme elle avait été embrassée par chois.  Le sceau de la perpetiuté obligatoire, ce fut Basile qui l’imprima; c’est à lui réellement que remonte, comme règlé commune, et comme habitude générale, l’institution des vœux perpétuels.  Helyot, Hist. des ordres monastiques, i. § 3, Bultean, Hist. des moines d’orient, p. 402, Montalembert, Hist. des moines d’occident, i. 105, s’accordent à reconnaitre que l’usage général des vœux perpétuels remonte à St. Basil.”  To St. Basil’s posthumous influence the system may be due.  But it seems questionable whether St. Basil’s Rule included formal vows of perpetual obligation in the more modern sense.  I am not quite sure that the passages cited fully bear this out.  Is the earnest exhortation not to quit the holier life consistent with a binding pledge?  Would not a more distinctly authoritative tone be adopted?  cf. Letters xlv. and xlvi.  It is plain that a reminder was needed, and that the plea was possible that the profession had not the binding force of matrimony.  The line taken is rather that a monk or nun ought to remain in his or her profession, and that it is a grievous sin to abandon it, than that there is an irrevocable contract.  So in the Sermo asceticus (it is not universally accepted), printed by Garnier between the Moralia and the Regulæ, it is said:  “Before the profession of the religious life, any one is at liberty to get the good of this life, in accordance with law and custom, and to give himself to the yoke of wedlock.  But when he has been enlisted, of his own consent, it is fitting (προσήκει) that he keep himself for God, as one of the sacred offerings, so that he may not risk incurring the damnation of sacrilege, by defiling in the service of this world the body consecrated by promise to God.”  This προσήκει is repeated in the Regulæ.  Basil’s monk, says Fialon (Et. Hist., p. 49) was irrevocably bound by the laws of the Church, by public opinion, and, still more, by his conscience.  It is to the last that the founder of the organisation seems to appeal.  In Letter xlvi. the reproach is not addressed merely to a “religieuse échappé de son cloitre,” as De Broglie has it, but to a nun guilty of unchastity.  Vows of virginity were among the earliest of religious obligations.  (cf. J. Martyr, Apol. i. 15, Athenvaras, Legat. 32, Origen, C. Celsum. vii. 48.) Basil (Can. xviii.) punishes a breach of the vow of virginity as he does adultery, but it was not till the Benedictine rule was established in Europe that it was generally regarded as absolutely irrevocable.  (cf. D.C.A. s.v. “Nun,” ii. p. 1411, and H. C. Lea’s History of Celibacy, Philadelphia, 1867.)  As a matter of fact, Basil’s cœnobitic monasticism, in comparison with the “wilder and more dreamy asceticism which prevailed in Egypt and Syria” (Milman, Hist. Christ. iii. 109), was “far more moderate and practical.”  It was a community of self-denying practical beneficence.  Work and worship were to aid one another.  This was the highest life, and to quit it was desertion of and disloyalty to neighbour and God.  To Basil, is it not rather the violation of holiness than the technical breach of a formal vow which is sacrilege?  Lea (p. 101) quotes Epiphanius (Panar. 61) as saying that it was better for a lapsed monk to take a lawful wife and be reconciled to the church through Penance.  Basil in Can. lx. (p. 256) contemplates a similar reconciliation.