No one will deny that the root ecumenical question is the nature of the Church. It is possible to deal with and even to liquidate certain surface differences between the churches; yet, since the separation is essentially ecclesiological, Christians of various persuasions find themselves worlds apart in their attempts to answer the question, what is the Church?The fact, therefore, that Karl Barth makes a systematic attempt to answer this question is not without importance; for this present-day Swiss Neo-Calvinist theologian certainly represents something serious in contemporary Protestant thought. Although it might be somewhat of an exaggeration to say that all Protestant theology today is defined either in accord with or in opposition to the theology of Karl Barth, nevertheless, as a contemporary spokesman for that "magisterium of the university professors" which is characteristic of Protestantism from its very beginnings, the theologian of Basel holds a position which is scarcely rivaled by any other Protestant thinker at the present time.When the mystery of the Church is the topic of discussion, whether or not from the point of view of Karl Barth, certain difficulties will be encountered. Ecclesiology is a "derived" system, in the sense that it is dependent upon other theological principles. Immediately primary among these, of course, is the doctrine concerning Christ, because it is with the Church of Christ that we are concerned. The presupposition, therefore, is that the question, what, or rather who, is Christ? is answered, before an attempt is made to ask, what is the Church?Another difficulty consists in this, that any systematic treatment of the mystery of the Church is bound to be synthetic, that is, it must embrace many facets of the theological discipline. It is impossible to say, for example, that ecclesiology is either solely dogmatic or moral. It all depends on whether the consideration is directed toward the structure or the life of the Church. Again, in either case, a complete ecclesiology must draw upon several of the tracts which go to make up either of these two parts of theology. This is just as true in the thought of Karl Barth as it is in the thought of a disciple of St. Thomas.Finally, those who have been born and/or nurtured in the Catholic tradition may find it strange to be moving in the thought system of a theologian who is not only Protestant but Neo-Protestant. It was probably true in the 625 at MCGILL UNIVERSITY LIBRARY on April 6, 2015 tsj.sagepub.com Downloaded from