The appointment of the Professor to the Convenership of the Committee on the Mission to the Jews in 1856 marked a new era in its history, in respect both of the method of its operations and the field in which these have ever since been carried on. One of the results of the Crimean war, which had then but recently closed, was the opening of the Turkish empire for evangelistic enterprise; and it may be said that the Professor laid the foundations of the Mission in the Levant at the several stations occupied by the Church of Scotland, which are now known not only as places of great historic interest but as important centres of missionary activity in which the Church bears an honourable part. In the autumn of 1857 he undertook a journey to the East at the request of the Committee, and in the course of his travels there visited not only the principal Turkish cities on the coast, but Jerusalem and other places in Palestine and Syria, collecting information with a view to find openings for the planting of the Mission at suitable stations in addition to the two which had been already occupied. The report which he presented on his return led by degrees to a great expansion of the Mission, and several of his own students and others were through his influence induced to enter the service of the Committee. With many other claims on his attention, he ungrudgingly gave up a great part of his time to the administration of the affairs of the Mission, over which for nineteen years he continued to preside with great zeal and wisdom, pressing its claims on the members of the Church, and guiding and encouraging the missionaries by an intelligent and sympathetic interest in their arduous work. When in 1875 he retired from the Convenership, the General Assembly expressed its sense of the value of the distinguished services which he had rendered to the Church in this department of her work in the following terms: "The Assembly are satisfied that the present prosperity of the Jewish Mission, and the remarkable progress which it has made, has been mainly owing to the great labour, the learning, enthusiasm, and warm and intelligent Christian interest which Dr Mitchell has devoted during these years to the cause of Jewish conversion in connection with the Church of Scotland." After his retirement from the Convenership he but seldom attended the meetings of the Committee, for the reason, as he was once heard to say, that he did not wish to appear to hamper his successors; but he never ceased to take a deep interest in the Mission, and none rejoiced more than he in its growing prosperity.
While the Professor still occupied the Hebrew Chair, he had shown a special aptitude for another branch of learning, in which he was yet to make a reputation for himself in the Churches not only of Britain but of America. In 1866 he published a lecture, primarily addressed to his students, on 'The Westminster Confession of Faith: A Contribution to the Study of its Historical Relations and to the Defence of its Teaching,' which, as a reply to views then current in certain quarters, attracted no little notice at the time of its publication, and which is not only of special interest as illustrating his theological standpoint, and the calm and temperate, yet earnest and vigorous, manner in which he could defend it, but is of permanent value as a contribution to the literature of the subject with which it deals. In the following year he published 'The Wedderburns and their Work, or the Sacred Poetry of the Scottish Reformation in its Relation to that of Germany'—a subject which was treated by him much more fully in one of his most recent works.
The Professor was known to possess a most extensive and accurate knowledge of Church History in general, and of Scottish Church History in particular; and when in 1868 he was called to occupy the Chair of Ecclesiastical History in St Mary's College, the appointment was hailed with satisfaction alike by the University and the Church. With an absorbing interest in his subject, and with the true instinct of the historian, he was most painstaking in ascertaining historical facts, never reaching his conclusions but as the result of patient and careful investigation; and those who knew him intimately can tell how little he grudged the trouble of a journey to Edinburgh or London, or even of an occasional excursion to the Continent, in order to prosecute his researches in libraries there with the view of verifying a statement, or of obtaining indubitable evidence on some controverted point. Besides those who had the privilege of listening to his prelections from the professorial chair, there are many in the Churches on both sides of the Atlantic who have profited by his great erudition; and his published writings, which all bear the impress of a master-hand, will always be reckoned standard works in Ecclesiastical History.
It is no part of the purpose of this notice to describe his various works in detail, but the mere enumeration of them will show what a life of unremitting study he lived. Besides those already referred to, he edited, along with the late Dr Struthers, in 1874, 'The Minutes of the Westminster Assembly from November 1644 to March 1649,' to which is prefixed an elaborate Historical Introduction written by himself; in 1882 he wrote a 'Historical Notice of Archbishop Hamilton's Catechism' (first printed at St Andrews in 1551), prefixed to Paterson's black-letter reprint of the same; in 1883 he published his Baird Lecture, 'The Westminster Assembly: Its History and Standards'; in 1886 he published 'The Catechisms of the Second Reformation'; in 1888 he edited, for the Scottish Text Society, 'The Richt Vay to the Kingdome of Heuine,' by John Gau, the earliest known prose-treatise in the Scottish dialect setting forth the doctrines of the Reformers; and in 1897, for the same Society, 'The Gude and Godlie Ballads,' reprinted from the edition of 1567, with a full and most interesting Introduction. For the Scottish History Society he also edited in 1892 and 1896, along with the writer of this sketch, two volumes of 'The Records of the Commissions of the General Assembly,' covering the period 1646-1650, from the original manuscript in the Assembly library, with an introduction, notes, and appendices by himself. To these must be added the present volume of the Baird Lecture, 'The Scottish Reformation.'
The Baird Lecture on the Westminster Assembly was received with great favour in America as well as in this country, and a new edition of it was published at Philadelphia in 1897, in a notice of which in the 'Presbyterian and Reformed Review' the following statement occurs: "The book at once took its rank as the most trustworthy and sympathetic account of the Westminster Standards in existence, and rapidly ran out of print. The public is to be congratulated that Dr Mitchell has permitted himself to be persuaded by the [Presbyterian] Board to revise the text and allow a new edition to be issued to meet the present demand. The revision does not much alter the text. A phrase is more felicitously turned here or rendered a shade more exact or emphatic there; a few additional references are added in the notes; and a few additional citations and remarks incorporated in them: that is about all. But so good a book needed only these little touches of betterment."
The Professor also contributed to various journals and encyclopædias many important articles, chiefly on historical topics relating to Scotland, which, if collected, would form a volume of miscellaneous papers of great interest and value. The most important of these are included in the subjoined list: In the 'British and Foreign Evangelical Review,' January 1872, "Our Scottish Reformation: Its Distinctive Characteristics and Present-Day Lessons," pp. 87-128; October 1875, "Dr Merle D'Aubigné on the Reformation in Scotland," pp. 736-760; October 1876, "Killen's Ecclesiastical History of Ireland," pp. 713-741: in the 'Catholic Presbyterian,' March 1879, "Calvin and the Psalmody of the Reformed Churches": in the 'Scottish Church,' November 1886, "St Andrews in Covenanting Times": in the 'Year-Book of the Church of Scotland,' 1886, "Brief Sketch of the History of the Reformed Church of Scotland": in 'St Giles' Lectures,' First Series, 1880-81, "Pre-Reformation Scotland"; and in Fourth Series, 1883-84, "The Primitive or Apostolic and Sub-Apostolic Church," being the first of the lectures entitled, "The Churches of Christendom." To Dr Schaff's Encyclopædia he contributed separate articles on "St Columba," "The Culdees," "Patrick Hamilton," "Iona," and "The Keltic Church"; and to the 'Presbyterian and Reformed Review,' published at Philadelphia, he contributed a review of Dr Hume Brown's 'John Knox.' Besides many Reports on various matters presented to the General Assembly, he issued for special purposes a "Statement regarding the Eldership," and a "List of Acts of the Scottish Parliament, and of Acts, Overtures, and Resolutions of the General Assembly of the Church of Scotland, adopted at various times for the Acknowledgment of the True Reformed Protestant Religion, the Maintenance of Sound Doctrine, and the Subscription of the Confessions of Faith of 1560 and 1647." When at Geneva, on one of his visits to the Continent, he prepared for private circulation, from the original, which is still preserved among the historical treasures in the Hotel de Ville, "Livre Des Anglois, or Register of the English Church at Geneva under the pastoral care of Knox and Goodman, 1555-1559," with a Prefatory Notice and a Facsimile of pp. 49, 50. To this list of his minor works may be added a sermon on "The Unsearchable Riches of Christ," published in 1879.
The Professor accorded a generous and helpful sympathy to those who were workers in the field in which he laboured himself with so great assiduity and success; and he was not only a member both of the Scottish History Society and of the Scottish Text Society, but took an active interest in their affairs. He was also one of the representatives of the Church of Scotland in the General Presbyterian Alliance from the date of its formation, and took part in the business of all its General Councils, at the first of which, held at Edinburgh in 1877, he laid on the table a paper which he had drawn up on "The Harmony between the Bibliology of the Westminster Confession and that of the earlier Reformed Confessions, exhibited in parallel columns." He was appointed Convener of the Committee on the Desiderata of the History of the Presbyterian Churches; and at the following General Council, held at Philadelphia in 1880, it fell to him, in consequence of the death of Principal Lorimer, who was Convener of the British section of the Committee on Creeds and Formulas of Subscription, to give in the report containing "Answers to Queries regarding Creeds and Confessions." The Answers as regards the Church of Scotland, which had been prepared by himself, are to be found in the Report of the Proceedings of the Council, pp. 969-984. When in America he also delivered a course of lectures at Alleghany. His connection with the Alliance brought him into close contact with some of the leading Presbyterian divines of Britain and America, with whom his opinions on the history of the doctrine, worship, and government of the Church carried great weight; and Dr Schaff has acknowledged his obligations to him, among others, in his well-known work entitled 'The Creeds of Christendom.'
In 1885 the Church showed her appreciation of the Professor's character and work by electing him to the Moderatorship of the General Assembly, an office which he filled with a union of dignity and authority which reflected honour upon the Church. If there are parties in the Church of Scotland, he never identified himself with any of them, and had learned to call no man master but Christ. He knew his own mind, and could give forcible expression to his convictions when occasion required. Naturally of an unassuming disposition and unobtrusive manners, he never courted popularity nor sought to thrust his opinions upon others; and it was for this reason, perhaps, that he was deferred to even by those whose views were in some respects widely divergent from his. It was doubtless for this reason also, as well as for others, that he wielded so great an influence in the counsels of the Church, and probably few men had more to do than he with the shaping of her policy in recent years. In paying a tribute to his memory at a meeting of the Presbytery of Edinburgh a few days after his decease, the Very Rev. Dr Scott of St George's said that "by Professor Mitchell's death the Church had lost a laborious, faithful, successful, and honoured minister and professor, and perhaps one of the soundest and wisest counsellors that the Church ever had. He was a man who had friends in all the Churches. He knew how powerfully his influence had told in the Church—always for conciliation, not only so far as those without their own Church were concerned, but those within the Church also. Had it not been for Dr Mitchell's influence the relaxation of the formula regarding the subscription of elders would never have been carried through."
A man of a very catholic spirit, and a lover of peace and concord, the Professor, like many others who longed for a comprehensive union of the Scottish Churches, would willingly have made all reasonable concessions for the attainment of so desirable an object. But he was too loyal a son of the Church of Scotland to consent to any unworthy compromise, and in the hour of danger no one was more ready than he to exert all the influence at his command in her defence. Readers of Dr Boyd's 'Twenty-five Years of St Andrews' may remember the account there given of the impression made by the Professor's sermon in the Town Church in the height of the contest in 1885, when the question of Disestablishment was brought so prominently before the electors of the St Andrews Burghs. Dr Boyd says: "It had been intimated at the services during the day that Dr Mitchell, our Professor of Church History, would lecture in the parish church in the evening on 'Some aspects of the Church Question deserving of consideration in the present crisis.' Dr Mitchell was that year Moderator of the Kirk: and he very seldom preaches. The church was filled by a great congregation. I should not in the least degree have been surprised to hear Dr Mitchell preach wisely and devoutly: that is his usual way. But it did surprise me to find that man of calm and well-balanced mind fire up into a pathos and vehemence which I have rarely seen equalled and never surpassed. The question of disestablishment had been raised: and one was made to realise how it stirs the blood of good men here. And not merely were there this evening a fire, a keenness, a power of stirring a multitude to the depth of their nature, which are rare indeed, but an incisive severity of denunciation which few had expected from that calm, cautious man. And if the preacher was at white-heat, so was the congregation long before he was done. Several times there would have been loud applause, had it not been hushed."
The attitude which the Professor maintained in regard to the doctrine and worship of the Church was a strictly conservative one, and may be best described in his own words, taken from an article included in the list of his minor works. In that article, after quoting the advice tendered by an eminent minister of the Church of England to a minister of the Church of Scotland—"Stick by your own Kirk: it is an honest Kirk, one of the few that has fairly rid itself of sacerdotalism and ritualism, and you have no cause to be ashamed of it"—he goes on to say: "The advice is not unneeded in the present day by others than he to whom it was originally tendered, and I give it this publicity for the benefit of all whom it may concern. The Reformed Church of Scotland from the first rid herself of these medieval corruptions, and the attempt to bring her again under the yoke issued in dire disaster to those who made it. This surely is no time for the Presbyterian Churches to swerve from the testimony they have so long and resolutely borne against all such errors. When we think of the mischief they are now causing in the Church of England, and the grief they are occasioning to many of her most loyal sons, rather does it become us to bear more decided testimony to the truths, that under the New Testament there is but one Priest, who ever liveth to make intercession for us, and one sacrifice once offered, which perfects for ever them that are sanctified; that He has not communicated His priestly office to His ministers either by succession or delegation, nor authorised them to repeat or continue that sacrifice which is the propitiation for sin; and that He has neither Himself imposed, nor warranted others to impose, a load of 'fondly' invented ceremonies in His worship."