“And in this, that philosophy begins in wonder [Plato, Theaetetus 155d], lies the, so to speak, non-bourgeois character of philosophy; for to feel astonishment and wonder is something non-bourgeois (if we can be allowed, for a moment, to use this all-too-easy terminology). For what does it mean to become bourgeois in the intellectual sense? More than anything else, it means that someone takes one's immediate surroundings (the world determined by the immediate purposes of life) so "tightly" and "densely," as if bearing an ultimate value, that the things of experience no longer become transparent. The greater, deeper, more real, and (at first) invisible world of essences is no longer even suspected to exist; the "wonder" is no longer there, it has no place to come from; the human being can no longer feel wonder. The commonplace mind, rendered deaf-mute, finds everything self-explanatory. But what really is self-explanatory? Is it self-explanatory, then, that we exist? Is it self-explanatory that there is such a thing as "seeing"? These are questions that someone who is locked into the daily world cannot ask; and that is so because such a person has not succeeded, as anyone whose senses (like a deaf person) are simply not functioning — has not managed even for once to forget the immediate needs of life, whereas the one who experiences wonder is one who, astounded by the deeper aspect of the world, cannot hear the immediate demands of life — if even for a moment, that moment when he gazes on the astounding vision of the world.”

translated as The Cost of Discipleship (1959), p. 51.
Discipleship (1937), Costly Grace
Context: The antithesis between the Christian life and the life of bourgeois respectability is at an end. The Christian life comes to mean nothing more than living in the world and as the world, in being no different from the world, in fact, in being prohibited from being different from the world for the sake of grace. The upshot of it all is that my only duty as a Christian is to leave the world for an hour or so on a Sunday morning and go to church to be assured that my sins are all forgiven. I need no longer try to follow Christ, for cheap grace, the bitterest foe of discipleship, which true discipleship must loathe and detest, has freed me from that.

(describing Marx’s view), p. 35.
Capitalism and Modern Social Theory (1971)

Dummett, M. A. E. The Logical Basis of Metaphysics. Cambridge: Harvard University Press. 1991.

Theaetetus, 155d
Plato, Theaetetus

155, The Dialogues of Plato, Volume 3, 1871, p. 377 http://books.google.com/books?id=4kQNAAAAIAAJ&pg=PA377
Theaetetus

Source: Correspondence, Letters to George Sand, 10 May 1867

Source: Life is Elsewhere

Source: Leisure, the Basis of Culture (1948), The Philosophical Act, pp. 127–128
The "interpretation of Plato" referred to is that of Gerhard Krüger, Einsicht und Leidenschaft (Frankfurt, 1939), p. 301.

Source: Kritik der zynischen Vernunft [Critique of Cynical Reason] (1983), pp. 63-64