In one of his early works, A Private and Public Faith, theological polemics at their best, William Stringfellow charts in compact yet elliptical prose the relationship between Christian witness and the presence of the grace of God in the secularity of the world.
The cohesion and commonality of the vocation of Christians originates in their power to discern the truth of the word of God in any event whatever, and precisely because the Word of God is present in all events that power may be exercised in any event... No man - for that matter, no creature, no idea, no institution, no nation, no issue, no action - is beyond the reach and intercession of some member of the Body of Christ. It is in this way, indeed, that is by the width and the depth of the implication of Christians in the life of the world, that the unequivocal fact of grace is communicated, that the universality of Christ is represented and that the ubiquity of the Word of God is exposed.
For lay folk in the Church this means that there is no forbidden work. There is no corner of human existence, however degraded or neglected into which they may not venture; no person however beleaguered or possessed whom they may not befriend or represent; no cause, however vain, or stupid in which they may not witness; no risk, however costly or imprudent which they may not undertake.
This intimacy with the world as it is, this peculiar freedom, this awful innocence towards the world which a Christian is given is what makes Christian look like a sucker. He looks like that to other men because he is engaged in the wholesale expenditure of his life.
A Christian is not distinguished by his political views or moral decision, or habitual conduct or personal piety, or least of all by his churchly activities, A Christian is distinguished by his radical esteem for the Incarnation ... by his reverence for the life of God in the whole of creation, even and in a sense especially in the travail of sin.The characteristic place to find a Christian is among his enemies. The first place to look for Christ is in Hell. (pp.42-43 A Private and a Public Faith)
For links with access to resources by and about Stringfellow see: Stringfellow - Ethics and Theology and the archives of Ben Myers Blog Faith and Theology March 2009.