I was reminded today of this passage from Jacques Ellul's The Politics of God and the Politics of Man (my italics):
The action we attempt will always be regarded by the world as a failure, and the more so the more it is authentically faithful. We cannot be successful or show the church to be effective in the world unless we adopt the world's criterion of efficacy, which means adopting its means as well.
As the world sees it, action which is faithful to God will always fail, just as Jesus Christ necessarily went to the cross. Such action always leads to a dead end. It is always a fiasco from the standpoint of worldly power. But this should not worry us. It does not mean that our action is in truth ineffectual. Efficacy measured in terms of faithfulness cannot be compared at any point with efficacy measured in terms of success.
...These successes, this efficacy as it would be called from man's standpoint, and especially in our own society, will never amount to anything more than the approval given by the world, by society, to certain acts and means. It is the stamp of a group of men, a social body. But if we do not believe that society is good and right, this approval proves nothing except that the action is in conformity with the world. It does not mean that the world has changed; quite the contrary. Each time the people of God becomes effective according to the world's criteria, this only implies that society has absorbed our action and is using it for its own ends and for its own profit. ...The efficacy we think we have is simply a power in the world's service, for the perfecting of its own being, for its better organization....
There can be no question of securing the approval of the world or its conformity to us. ...We have simply to be, and we can only be a question put within the world, a question invincibly confronting it. This is our efficacy. It is the efficacy of the question, a question which society and sociological movements cannot assimilate. Israel and the church have never been efficacious except to the degree that the world has been unable to assimilate them. This is the vocation of the people of God incomparably more authentic than "service" or "works."
It is not at the level of works and their results that this efficacy may be seen; it is at the level of inassimilability.