Bryan Appleyard is talking to John Berger, and in the course of their conversation there's this:
He remains a Marxist, but with a crucial note of dissent. "The problem with Marxism is there is no real space for ethics. Okay, there is plenty of space in it for the struggle of justice against injustice, but the notion that an act is good or bad in itself - there is no space for that. There is no space for that which is outside time or, if you wish, for the eternal... There is the possibility of it being combined with another philosophical view which is not simply materialist."
I think that sums things up quite well. In its classical and standard forms Marxism made no real space for ethics; it gave no explicit or independent weight to the political importance of moral principles. Worse than that, some of its most famous thinkers, starting with Marx himself, mocked any overt appeal to morality, and Marxists have often disguised from themselves even - what is manifest in Marxist critical argument, again starting from Marx himself - that the movement against capitalism always had at its core (as Berger says) a commitment to justice. These tendencies were obviously a weakness of the tradition and they contributed their share to the descent of Marxist parties and movements into dictatorial and morally criminal ways.
In what he says here, however, Berger indicates something else. For an empty space need only remain empty so long as one fails to see in it, also, an opening. In the hands of those who considered Marxism a complete system containing answers to every kind of question, the absence of an ethics was a plain deficiency. It rendered such adherents more vulnerable to forms of careless or cynical instrumentalism than they would otherwise have been. But Marxism never was an all-encompassing system, despite what has sometimes been claimed for it. It sought to explain certain things and to project tendencies (of development) on that basis. Some of this it did well and some of it not so well. But the empty spaces within Marxist modes of thinking didn't, and don't, have to be left empty. There is the possibility of, precisely, combining Marxism with other philosophical views - of trying to fill the spaces; or, to put the same thing differently, of using them as spaces in which to think rather than pretending to have answers to questions when you don't. This is, in fact, more than a possibility; for those who think that Marxism tells you something true about the world, provides useful ways of analysing it, it's a necessity.