Epistle XLII. To Eusebius, Archbishop of Thessalonica. Gregory to Eusebius, &c. If, most dear brother, we consider attentively how great is the excellence of peace, we shall recognize with what earnestness it should be cultivated by us.  For indeed our Lord and Redeemer vouchsafed to leave and give it as a great boon to His disciples, that He might thereby make those who were united to Him in firmness of faith His associates in loving participation with Himself.  For it is written, Blessed are the peacemakers, for they shall be called the children of God ( Matth. v. 9 ).  Whosoever, then, desires to be the father’s heir, let him, by keeping peace, not refuse to be his child.  For he who gives place to discord surely makes himself to be without lot in so great a gift.  Seeing then that by the mercy of God the purity of thy faith has been declared to us, as was meet, with catholic rectitude, we are taken up with great surprise that thou shouldest suffer those whom thou knowest to believe well and to think aright to be needlessly scandalised by the fault of certain persons, so that the reputation of thy Fraternity is clouded by the guilt of others.  For how can one avoid suspicion of error who extends sufferance to them that are in error?  Or what estimate of himself can he expect, if he provides not for purging by open satisfaction what fervour of faith requires to be purged? For indeed it is said that Luke thy presbyter and Peter refuse to receive the Chalcedonian synod, and that on this account the hearts of thy orthodox children are perturbed with no slight offence 122 .  And, since their zeal is not only to be praised but also to be altogether cherished, we exhort that the care of thy Fraternity hesitate not to investigate the matter with all activity and solicitude.  And, if those persons should be found innocent of that pravity, remove offence from the minds of thy children by giving them satisfaction, and among all heresies anathematise especially Severus and Nestorius, so that purification may engender charity among those with whom a sinister suspicion concerning those heretics has, out of love of the faith, produced dissension; and that one feeling of concord may salubriously knit together those whom a pure and single confession of catholic truth unites.  Nor let the doubters be thought unworthy of satisfaction, since we are instructed by the Divine voice, Despise not one of these who are the least ( Matth. xxviii. 18 ).  Whoso, then, desires not that he who instructs us should be despised, let him not reject the words of the instructor; since he also of whom our Redeemer testified that he was a vessel of election unto Himself admonishes us to keep the unity of the Spirit in the bond of peace ( Ephes. iv .).  Hence whosoever refuses not to be held by this bond of salvation, let him study the things that make for peace, and afford no place for the foe; so that, having been enabled to advance by the fierce dissension of brethren, he may be more stoutly trampled on, when unity is established. If however, as we do not expect, they should be found to be wounded by the dart of this error, the cure of ecclesiastical exhortation must be applied to them, so that they may either remain among the Lord’s sheep if healed, or be cut off from the unity of the ecclesiastical body; to the end that from a slight loss there may be a great gain, and that the removal of a part may make the whole body free.  For it is the care also of a provident shepherd not to delay casting out from consort with his sound sheep a sickly one that admits not of cure, lest it should contaminate others with the taint of its sickness, knowing that he cannot preserve the soundness of the rest but by the ejection of this one.  Accordingly I once more warn you in brotherly charity to investigate this matter with the utmost vigilance, and to observe what we have written with the utmost care, lest by consort with others you should make the right faith which you hold doubtful.  For he who does not correct things that should be cut off commits them.  Wherefore you must take thought with great solicitude and with great provision in all ways, that the persons of those men be not an offence to others, or common opinion injurious to you; that so a shepherd’s gains may accrue to your Fraternity from the sheep committed to you all the more as both sincere love and approved care shall have made you solicitous for their custody. 122     Those who refused to accept the condemnation of “The Three Chapters” by the fifth council alleged that it contravened the Council of Chalcedon.  It may be that the persons referred to here, in their defence of what had been decreed in the fifth council, had seemed to admit that it did contravene the fourth, which they consequently were supposed to reject.