In the dogmatic and theological history of every age, not excluding that of Protestantism, secular factors have played a part which tends to cover over all else. For all the gloating with which it was done, it was a good thing that the work of Pietism and the Enlightenment in Church History established so incontrovertibly the fact that even in such periods of supreme decision as that in which the dogma of the Trinity arose the history of the Church was anything but a history of heroes and saints. Yet in this case we should be just and perceptive and allow that not only the Church of Byzantium but also that of Wittenberg and Geneva, and finally the purest Church of any of the quiet in the land, have always and everywhere been, when examined at close range, centres of frailties and scandals of every kind, and that on the basis of the Reformation doctrine of justification at all events it is neither fitting nor worth while to play off the worldliness of the Church against the seriousness of the insights it has perhaps gained in spite of and in this worldliness. The same may be said about the indisputable connexion of the dogma with the philosophy of the age. By proving philosophical involvement we can reject the confessions and theology of any age and school, and we can do this the more effectively the less we see the beam in our own eye. For linguistically theologians have always depended on some philosophy and linguistically they always will. But instead of getting Pharisaically indignant about this and consigning whole periods to the limbo of a philosophy that is supposed to deny the Gospel—simply because our own philosophy is different—it is better to stick strictly to the one question what the theologians of the earlier period were really trying to say in the vocabulary of their philosophy. Caution is especially demanded when we insist on differences in the so-called piety of different periods and therefore claim that the piety out of which the dogma of the Trinity arose was completely different from our own piety with its sober focus, as they said some years ago, on “worldview and morality.” What right have we to regard our own piety, even if its agreement with the Reformation and the New Testament seem ever so impeccable, as the only piety that is possible in the Church, and therefore to exalt it as a standard by which to measure the insights of past ages? Let us be sure of our own cause so far as we can. But antithetical rigidity especially in evaluating the subjective religion of others is something against which we can only issue a warning.

— Karl Barth, CD I/1, 377–78