'New materialism' as a cohesive body of thought doesn't exist and 'flat ontology' is a monumental red herring. Andrew Barry made the former point very well in a panel on Sunday afternoon. He very much voiced what I was thinking but I will try to expand on that.
Saying that there are new materialisms might be a step in the right direction but it's still not good enough if the analysis then continues to proceed on the basis of lowest common denominators (many of which are erroneously identified). For many of the thinkers who are being frequently identified by that term, it is quite questionable whether they are materialists at all. The metaphysics of Alfred North Whitehead, for example, is often referred to as materialist (didn't hear that at this conference but have done in the past) but what can this mean when he did not base his ontology on a conception of matter but rather of events (or rather 'actual occasions')? Latour himself has flirted with the term 'materialist' but this is far from a simple relationship (he is comfortably more Whiteheadist than materialist, by any reasonable estimation).
Being not-an-idealist is not the same as being a materialist – it is not an either/or equation. The presumption that we must all choose between these two preset options is a death blow to the possibility of thought. It's just much more complicated than that.
The loose family resemblance that the term new materialism identifies cannot serve as a starting point for any meaningful analysis or critique. That requires grappling with particular thinkers in their particularity. And that is a much more difficult task than casting around vague aspersions but it's also the only way to actually say anything. (Of course, the pressures of the 10 minute conference presentation tend to work against any and all forms of incisiveness and subtlety but nevertheless.)
Having said all of that, there are a handful of thinkers who place themselves under the flag of 'new materialism' and I don't wish to disparage whatever that term is doing for them. However, as the term is circulating within International Relations conversations (and to a large extent within human geography as well), I think it is quite clear what that term is doing there: shoehorning a rather varied range of thinkers into a neat-ish box that can be broadly and abstractly discussed on the basis of a handful of alleged, half-articulated lowest common denominators. It is all about dumbing down the conversation.
That may be a bit harsh but only a bit.
(I should add at this point that I am not aiming these comments at anyone in particular but at the general level of conversation around these issues. Those promoting new materialism and flat ontology might be as guilty as those criticising these terms, in this respect.)
I hasten to add also that I have nothing against '-isms' and other heuristic devices that allow the complexities of intellectual affiliations and trends to be signposted and made navigable. However, academics have a deeply unhealthy relationship with -isms, turns and the like. In IR, in particular, there is a long history of obsessing over trends and movements rather than authors and arguments. It's never innocent and always involves the suppression of various aspects of the landscape of possible thought.
If that sounds like rather a 'poststructuralist' thing to say (it may well do) then that term itself, I would argue, is not at all exempt from these problems. What was at stake in privileging structural linguistics in the intellectual inheritances of those authors grouped under the term 'poststructuralist' (they were all much more than this)? I have my theories. The main one is that this made it easier to turn a complex set of ideas into a 'theoretical framework' that could be taught, textbooked and 'applied.' But I digress.
Secondly, flat ontology. Until recently I had forgotten that this was a 'thing.' It gets thrown around in a variety of ways without what it's supposed to actually mean being made particularly clear in any given instance. More and more it seems to be used as a polemical tool which suggests that the likes of Actor-Network Theory flatten out all forms of hierarchy and have, therefore, no perception of or interest in questions of power and inequality (although see also). This rests on a conflation of ontology and method.
In ANT (itself a somewhat diverse array of scholars but, I think, just about cohesive enough to make the designation meaningful) it is an important principle of method that one does not presuppose that which one is attempting to account for. Thus, ANT effects a flattening of the social field in the sense that pre-established hierarchies and verticalities are not what is used to explain events on a level of generality but what is to be explained in terms of the specificity of each observed hierarchy.
Take a scientific fact. A fact that has won out over its rivals and been enshrined in textbooks, encyclopaedias, people's general knowledge, etc. Plainly, the situation I am describing is not 'flat' in the sense of there being no hierarchy. It is precisely because there is hierarchy that one should not take hierarchies for granted. The hierarchy is the thing that one wishes to explain and this explanation comes from an intensive description of the process by which human and non-human agencies are criss-crossed and assembled, each affecting and perturbing the overall formation as they are enrolled into it. That is, the hierarchy is assembled from a heterogeneous array of forces that one can never a priori place in a pre-given hierarchy. The field that is to produce the descriptive explanation is flattened insofar as order is not to be taken for granted and no one case is to be made the archetype for all other cases. That's all.
That doesn't mean that this approach is necessarily right or that it is universally applicable (I don't think that it is) but that it should be understood for what it is – at least as much about method as about ontology per se.
Relatedly, this is what Latour has to say about power in a recent interview. They don't use the term flat ontology but it could be easily read into the question.
– VD: We want to ask you about power. If we assume that ontologies are multiple and relational, where do we locate differences and power asymmetries? There has been a lot of criticism, especially in Latin America, that this idea of multiplicity erases conflict, hegemony, domination and asymmetries. So how would you answer to this criticism and include questions on asymmetries and power?
– BL: I think you have to reverse the question and ask: when do people use the notions of power and asymmetry? What is the landscape that we imagine as the ideal? I always suspect when the landscape we imagine as the ideal is flat, where there would be no power relations and where all relations would be symmetrical. Behind the notion of power is the idea that power is something that should not be carried out, that it is a sort of deviation from the path represented by something we have in mind that is probably reason, or solidarity, or peacefulness. However, people like me never believe in peacefulness as symmetry. I don’t use so much the notion of power, because asymmetry, in the landscape we try to describe, is everywhere. If you describe a mountain from here to Buenos Aires, you will need to follow one calibrated instrument and describe how this one instrument registers differences, what in my work is actor‑network theory (ANT). For example, we think the pampa is very flat and then we see it goes up and down! So, to register asymmetry you need a notion that doesnot use the word power because when you use power there is always this idea that you could actually get rid of it. That power has to disappear, that it is abnormal. But asymmetry is the nature of the landscape you are describing. Moreover, if you mean by multiplicity association in the ANT sense of the word, that is as heterogeneous connections, which have to be composed, it means you have to be amazingly precise on the nature of the asymmetry. That is, this man here or this woman there is actually producing, in this specific place, a pattern which is spreading in this way and which has to be attacked. Is this power? Yes, of course it is power. But power doesn’t add anything to that description. The primary problem of the notion of power is that it withdraws something from the description, because it says: “Ideally, we could do without power”. So power is a drug, it isa sort of poison that is used because people feel good about doing so, “Ah, I’m describing power relations”. But the problem is that they never do it because in fact they replace the analysis of the asymmetry in a specific place, where specific effects have been produced, by this sort of overall ideal. They assume that if they speak about power, the work already is done. But as long as you are not able to identify where danger is being produced and modified, abstain from using the notion of power. That is why I’m very suspicious about people who use power. It is basically a left over from the Left, an old idea that assumes that we should address power because they imagine that they could get rid of it.
– VD: Is it like a shortcut?
– BL: Yes. Could you imagine describing a landscape where there would be no power? Actually, I put power at the heart where it was not supposed to be: in science! So, I’m not impressed by those criticisms. Others put power everywhere, but not in science. And in science, where we show it, asymmetry is everywhere, the scientist that published this here and not there, etcetera, everything is completely asymmetrical in science. But then, it doesn’t mean that you have to add the notion of power. Because if you add it, what do you add? This is a question I have never understood. What is added by adding the notion of power? Yes, it is asymmetrical. It is like saying the Andes are high. Yes they are high. Now, if you want to walk it up and down you need lots of trucks. Where are the trucks, how do we mobilize them, which road do we take, which tools do we need to walk it up. These are the questions we have to ask.For Latour, power doesn't add to the description and is politically misleading, so out it goes. (Now, I think that there is still a need for a concept of power as a risk that any actor undertakes in channelling forces that might capture it but that's a topic for another day.)
What the ANT-type position does refuse at a properly ontological level is the dualist separation of nature/society, substructure/superstructure or anything of that sort (if that's what a 'flat ontology' is then, yes, it is flat – although it would be more accurate to say non-dualist). The critical realist separation between transitive and intransitive, for example, is, from this point of view, just another instance of the same old modernist bifurcation of nature, with a bit of a tweak. It is a depth ontology that operates on the basis of images of surface and subsurface, soil and bedrock, veil and reality. It's more of the same: the shallow ephemera of perception vs. the immutable depths of reality.
It is not so much that ANT et al. are 'flat' but rather that critical realism et al. are dualist (even if they sometimes claim not to be). The metaphor of depth carries within it the critique of flatness. To promote 'flat ontology' as a good thing is rather to promote a term of abuse. Neither flat nor deep – refuse the imposition of the choice.
So, yes, there are real and important differences to be identified and picked apart here, undoubtedly. But phrases like new materialism and flat ontology aren't nearly good enough to get at them. It's like trying to do heart surgery with a shovel.
Probably the principal difference to be picked apart, in my opinion, is the insistence upon empirical, idiographic, casuistic and descriptive studies. That is to say, the insistence that theory be what facilitates empirical research rather than being what substitutes for it, overlays it or provides the explanatory supplement that the things themselves lack; that studies focus intensively upon particular cases and attempt to understand them in their specificity, while at the same time accommodating their wider connectedness and historicity; that the only form of explanation should be a well-constructed description and that generalisation should be undercut at every opportunity.
These are principles that are eminently contestable and that would make for a conversation worth having. However, until we can get past such poorly constructed concepts that don't even make contact with the real disagreements, this will not happen.