As is usual in this introductory collection, this entry by Marcel Verweij is very compressed and yet covers a lot of ground, so I'll do what I've done mostly and offer a comment on a particular aspect of the discussion I think can do with some expansion. Verweij concerns himself with laying out some reasons to believe that general principles can't do all the work that needs to be done in applied ethics. Be that as it may, I believe that there is some work which principles of the most straightforward and forceful sort can accomplish, and that is to put constraints on what courses of action we could rightly pursue. Vermeij's presentation gives the impression that this wouldn't be the case, because principles are supposedly too abstract to give clear guidance in concrete cases. However, a thickly developed concept like 'always be honest' can do exactly that, I argue.
The main difficulty with working with principles, as Verweij rightly points out again and again, is that it isn't always straightforward to see what they would entail. However, this is a problem of vagueness rather than one concerning a principle's normative force: if you could be clear about exactly what the content of a principle is, this problem would disappear, or it would become clear that it wasn't as useful as it at first appeared. Perhaps the latter turns out to be true of every principle, but we should hesitate before we conclude as much. If we could determine what would count as fulfilling the demand of a principle, and what a clear failure would be like, that would meet the challenge to provide concrete guidance. Perhaps the principle wouldn't tell you which course of action would be uniquely right, but it would filter the options by rejecting a number of candidates which would simply be unacceptable on account of that principle: that is what I mean with principles placing constraints on what we should consider right action.
The principle of 'be honest', by which I mean 'never intentionally deceive someone so that on your account they reason from false grounds' is an excellent example of how this can be done, because it is a principle which is established in a number of independent ways. Firstly, it is a principle with enormous standing. It is the one clear success of Kant's categorical imperative, for instance: it is simply inconceivable to have a situation in which people communicate without most things they say being true, because that would only lead to a failure in communication. Doing the same but in an entirely different way, David Lewis gives an analysis and vindication of a convention of truth-telling, that is, the regularity of people telling the truth and expecting others to do so, on game-theoretic grounds. And, different again, Elizabeth Anscombe held that there simply are no situations in which it is right to lie, though not as an absolute prohibition, but as a matter of fact which drops out of the fact that each of us rely so heavily on what we tell each other that the goods we might gain from deceit could hardly be goods of moral worth. Secondly, what honesty demands of us is perfectly clear in almost every case. We know very well what it means to tell the truth, and because deceitfulness is predicated on deceitful intent, we can't help but know when we lie. That is, there are clear success conditions on being honest, and a precise way to tell when you're being deceitful. There are debates and difficult questions about how far you should pursue it: Kant's insistence that you should tell the truth even to an enquiring murderer might not impress most people, but everybody can (or damn-well should) agree that it is not good in itself to deceive other people, and that it is not bad in itself to furnish people with the truth. The degree to which a course of action demands deceit is the degree to which it is to be avoided, and the contrary: this isn't a complete decision procedure, but it is an informative and concrete constraint on action.
Perhaps it is a mistake to appeal to principles to settle the question of what you should do in such-and-such a situation, but it would be too quick to move from that to a conclusion that principles can't offer guidance in real cases. They might not tell you everything, but given the appropriate success and failure conditions, principles can tell you to some extent at least what it is you should do.