To start off proceedings, we have a little piece of meta-ethics: Paul van Tongeren writing on the birth of ethics in ancient Greece with Socrates, looking in particular to the first book of Plato's Republic, and Bo Pettersson trying to come to grips with what van Tongeren is saying. Pettersson's article is the important one (that is, it's the one that the course administrators took the trouble to print in a collection and mail to me), but it spends all of its time attempting to make sense of exactly what van Tongeren is saying, and I'll do the same. van Tongeren is doing meta-ethics in that he is investigating the conditions needed for ethical reflection to start in earnest. However, I'm unconvinced by his attempts to present two approaches as ones which end ethical reflection if we accept them. I find both of his targts, traditionalism and relativism, to have versions which contribute to rather than strangle ethical reflection.
van Tongeren's line as I understand it is as follows: the practice of ethics properly-so-called is ethical reflection; reflection is needed to navigate through uncertainty to some appropriate end; thus, for something to count as doing ethics, it needs to convincingly question whether some course of action is the right one. This requires the rejection of at least two approaches which could be taken to answer the question 'is this the right course of action?': traditionalism, which responds 'the right course is that which our ancestors would follow'; and relativism, which goes 'there is no matter of fact which course is right'. Keeping with his focus on the Republic, he identifies the former with Polemarchus, and the latter with Thrasymachus. He rejects the former because it denies that there is ethical uncertainty, and the latter because it gives up on seperating the right course of action from the wrong.
However, Thrasymachus does have a way to seperate right from wrong, as Pettersson rightly notes: what is right is what is to the advantage to the stronger party. I say he confuses a descriptive state of affairs for a normative one. I'm sure we can all agree that there is no end to situations where what people call justice is in fact that which is in the interest of the stronger party. The mistake is to think that what gets called justice actually is justice. People can be wrong, of course, and are perhaps especially likely to be wrong when those calling the shots have a conflict of interest, as it is if what gets called justice is what is in favour of the most powerful. But there is scope for an alternative, which Thrasymachus misses. Socrates refutes his position exactly by developing the alternative, that there are constraints of justice on what interests the powerful can pursue, and Thrasymachus leaves in a huff.
It is worthwhile to point out one version of relativism which is simply confused and would render ethics to nonsense were we to accept it: what counts as right for some group is what is considered right by that group. As Bernard Williams points out, this is simply a contradiction: if what is right for A is what A believes is right, then it is wrong for B to interfere with A, but this is an equivocation on 'right', because from the former relative use for A we have moved to a non-relative, inter-group use for B. This vulgar relativism is a contradiction because it gives both relative and non-relative scope to 'right'. Notice the difference between this position and that of Thrasymachus: he gives a way to pick out what would count as justice, and thus the correctness conditions for calling something right, whereas in vulgar relativism there are none. Because Thrasymachus's position makes an informative and falsifiable claim, it is a substantial ethical position. I must conclude that van Tongeren mischaracterises his target.
Matters are a little more interesting for van Tongeren's other target, traditionalism. I find van Tongeren's claim, that ethical reflection wasn't done in archaic conditions of extreme conservatism and a rigid caste system, simply incredible. I contend that you can accept the premise of van Tongeren's argument, that under a traditionalism every ethical question is answered by reference to established practice, and deny the conclusion, that accepting traditionalism makes an end to ethical enquiry. This is because I believe that there remains a question for ethical reflection if you accept traditionalism, and that is extending the traditional courses of action to novel situations. The type of widespread upheaval through war and intercultural contact van Tongeren points to would count as novel situations, but so would any state of affairs which isn't identical to some previous one which one's ancestor's faced and their response to which you do not explicitly know, thus, even under the archaic conditions of an entrenched caste society that van Tongeren considers, there still remain ethical questions which demand attention.
Traditionalism must be a theory about how to discover what is right rather than a theory of what rightness consists in: van Tongeren seems to say as much, and Pettersson is clear about it, but most strikingly, the Euthyphro problem makes it impossible for it to be otherwise. The Euthyphro problem concerns moral authority, and motivates this split between moral ontology and moral epistemology, so it is strikingly relevant: if some authority A says that X is right, it either is that A saying so makes X right, or that X is right independently of A saying so. In this case, as I imagine it is in every Euthyphro case, taking the first option is untenable: that would make traditionalism out to say 'whatever your ancestors did counts as right', which is a vulgar relativism and liable to the same objection. So considering what your ancestors did must be a way to learn what is right, rather than definitive of right.
What you learn through this traditionalist method is a list of actions which have been identified as right in virtue of your ancestors having done them. Let us set aside the issue that not everything your ancestors did would carry their seal of approval, because it is easy to make a set of traditionally approved actions, which would include the considered judgement that some things done by your ancestors turns out to have been wrong. I think this considered traditionalism gets much closer to what the view is supposed to be. An obvious consequence of this position is that if you ever are in a situation just like one your ancestors faced, you should do what they did. This, however, doesn't go very far. You never come across a situation exactly like a previous one, simply because your situation is later and thus has a different history at the very least. So there remains the question of what counts as similar in all the relevant ways. That is a tremendously weighty question. Any attempt to answer it means settling issues about what counts as morally salient facts, what dimensions those facts are found on, how to measure significant differences on those dimensions, and so on. Remember that it isn't that your ancestors had the power to make something right or wrong by fiat, it is just that you trust their judgement. What you need to do to make use of the store of precedents they gave you is to recreate, to some degree, the judgements they made, and see how your situation is relevantly similar and different from that of the precedent. Not only is this to embark on ethical reflection, it quite likely is paradigmatic of what ethical reflection consists in.
In entertaining traditionalism there is again an opportunity to slip from descriptive to normative states of affairs,which again would be a mistake. It isn't just that whatever your ancestors might have done, it is right, it is that there were constraints on their actions, and that in deciding on whether this or that is the right course of action, we are trying to decipher what those constraints are. This, again, is paradigmatic of ethical reflection.
There is of course a way in which Socratic debates show an innovation, but that seems to me to be in how ethical reflection is articulated, rather than the rather bizarre idea that only the type of questions Socrates asked counts as being reflective. Such articulation sharpens the debate, but it can't be all there is to the debate, because ultimately what is judged in ethics isn't what we say, but what we do.
In conclusion, regarding van Tongeren I believe that he has made a mistake in how he characterises Socrates's opponents in the first book of the Republic: he thinks there is a difference in kind between the type of position Socrates is after and the type his opponents offer, that only the Socratic one counts as suitably reflective; but instead I think that what is happening is that Socrates takes these commonly held views seriously and tests their mettle exactly as products of reflection. They turn out to fail, but no matter: almost every theory is false, after all. I think that relativism and traditionalism are not necessarily threats to ethics, but are to be entertained seriously. We can learn valuable things from considering them, like seeing the inconsistency of vulgar relativism which points to impotant issues about the scope of our judgements, and reflecting on the difficulties in following precedents even if we accept their authority.
There is one point in Pettersson's piece that I want to quickly draw attention to, where he admirably draws out certain tenets of the traditionalist and relativist strategies. Pettersson's conclusion is that there are two relativist tenets we should reject: we must deny that there are no true and definitive answers to ethical questions, and also deny that there is no method to discover such truths. I think relativism can get off the hook here, because it can join Petterrson in rejecting the former and still consistently maintain that there is no method to discover truth in ethics. To make this point, I want to distinguish between first- and second-level ethical concepts, much like Gottlob Frege does in his logic. The rightness and wrongness of actions and other such typical objects of ethics are first-level concepts for my purposes, and concepts which concern ones on the first level are second-level concepts. We can consistently embrace relativism as a second-level concept: it is an informative claim about the status of first-level concepts, that is, rightness and wrongness, which says that there is no fact of the matter about being right. It is informative, because it has implications and there are ways you could show it to be false. It is also a definitive answer to an ethical question. Given relativism, it is true that there is no fact of the matter on what counts as right and wrong. Thus, it's a substantive position which is appropriate to ethical reflection.
There are objections I can consider, but this post is already very long, so I'll rather stop here, and address further issues as they might arise in comments.