Of all great theologians Karl Barth lends himself perhaps least of all to any attempt at reconciliation on a superficial level, to a reconciliation which would obscure the basic differences between his position and that of his opponents. And yet, his work exerts a compulsion on his readers to rethink their positions in its light. It does this even more by the echoes it seems so often to contain of the judgment under which all human thinking stands, than by the challenge of its clarity and its authentically Christocentric character. The ‘confessional conversation’ to which his work cannot but give rise must proceed piecemeal, by patient and painstaking discussion of Christian theology topic by topic. I want to examine one particular topic of theological discussion in this paper: that of the nature and structure of theological thinking itself. I shall try to outline and to compare two of the most highly developed and consciously thought-out accounts of what theological thinking consists in: the accounts given by Barth, and by St. Thomas Aquinas. Fundamental though this question is, it is well to remind ourselves at the outset of its restricted canvas. For whatever convergence we may discover in the two accounts of what theological thinking is, there may be endless scope for divergence concerning some of the topics relevant to these accounts. I may instance those of the Bible, faith, revelation—all of them concepts central to our inquiry, yet concepts on which agreement can scarcely be taken for granted.