Karl Barth, Church Dogmatics 4.3.2, 881.
In the light of what we have already said, it is surely clear that before the end of all things there is no age whose work cannot be taken up again and continued and improved. Together with the whole ministry of the community, the critical scholarship of theology itself stands in constant need of criticism, correction and reform. For the same reason, it is inevitable that in constant self-testing it should be involved in continual warfare not so much with individual errorists as with the countless evil spirits of false or semi-false theology. To be sure, its weapons are those of "righteousness on the right hand and on the left" ( 2 Cor. 6.7), yet there can be no doubt as to the conflict. Always there must be serious questioning, analysis, argumentation, construction, discussion and therefore directly or indirectly, and preferably only indirectly, polemics. From time to time, though not all the time, a little of the notorious rabies theologorum [ed: theological madness] is thus in place.The long paragraph continues, however, on a more positive note:
This does not alter the fact, however, that in itself and as such theology is supremely positive and peaceable, that it fosters peace, and that it is thus to be pursued soberly, good-humouredly, without any nervous excitement, and particularly without too much petty, self-opinionated bickering. It is to be noted further that it is a modest undertaking which like missionary work can only aim to serve rather than to dominate by rendering a certain limited and transitory assistance to the cause of the community and therefore of all Christians and the world as a whole. It is to be noted further that when it is conceived and executed correctly and resolutely, yet also freely and modestly, theology is a singularly beautiful and joyful science (cf. C.D., II, 1, p. 656 f.), so that it is only willingly and cheerfully or not at all that we can be theologians.