From an article in j_spot (Volume 1, Issue 3) entitled 'Beyond Economy, or the Infinite Debt to the Other: Caputo and Derrida on Obligation and Responsibility' by Chris Anderson-Irwin.

Ethics is a problem in postmodernity. Thinking along Heideggerian lines, one might argue this problem started with Nietzsche's proclamation of the death of God and his critique of all values hitherto. But even Nietzsche shuddered a little at the thought of losing morality; he felt the coldness of space encroaching as the light of religion and its absolute values dimmed in 19th century Europe ...Nietzsche is all too often understood as heralding a Dionysian modern era, but he was also a self acknowledged heir to "the ascetic" tradition of Western morality)... If even Nietzsche feared the repercussions of letting ethics go, what about the rest of us?

Anderson-Irwin continues:

But what else is to be done if the foundations of ethics have been swept away, if every cultural, historical, theological or metaphysical support has been called into question? What is to be done if there is no knowledge in ethics, no certainty, no absolutes, no saving laws or formulas which solve all problems before they begin?

These questions are a rhetorical trick. Anderson-Irwin doen't mean to adress them. He's talking about a modernist ethics.

He says:

Perhaps the situation is not as dire as that. There is something suspicious about this assessment of the state of ethics. It seems too easy to say that ethics once dealt strictly with what could be "cognized" as objectively certain and universally true, whereas now, after Nietzsche, after Heidegger, after the end of Western metaphysics, we find ourselves in a precarious situation. ...The problem of ethics in postmodernity may have more to do with the way contemporary theorists tend to think of ethics. It has become common to connect ethics with cognition, designating it as a form of knowledge to be grasped by the cognitive subject. This view of ethics presupposes that there was once certainty, well-cleared ground, precise formulas and consensus regarding their legitimacy, but that since the cognitive subject has been knocked off its pedestal, a hole as been left at the centre of all of these schemes.

t has become common to connect ethics with cognition, designating it as a form of knowledge to be grasped by the cognitive subject. This view of ethics presupposes that there was once certainty, well-cleared ground, precise formulas and consensus regarding their legitimacy, but that since the cognitive subject has been knocked off its pedestal, a hole as been left at the centre of all of these schemes. On this view, the loss of certain knowledge leads to the destabilization of ethics, and to a certain amount of hand-wringing: How are ethics to be conceived if not as a matter of knowledge? Are we not lost on a sea of radical heteronomy where any number of approaches to ethics drift beside one another, sometimes colliding when the weather gets rough? This loss of a ballast seems to leave us with what Jameson calls a postmodern antinomy.... a situation where on the one hand there can be no ethical certainty while on the other we find ourselves treating ethics as an important question, and, even more significantly, relying on and presupposing at least a rudimentary or minimal set of ethical conditions that structure the relationships between persons.