¹ See below for a brief discussion of the merits of using the notion of ‘realm’, that arguably carries comparatively little theoretical baggage.

² Which is not to hide that it is not also a piece on the process of an ongoing conversation between its authors.

³ Or from identifying itself as a social science in the first place. See Jackson, Patrick, The Conduct of Inquiry in International Relations: Philosophy of Science and its Implications for the Study of World Politics (London: Routledge, 2011)Google Scholar and Aalto, Pami, Vilho, Harle, and Moisio, Sami (eds), International Studies: Interdisciplinary Approaches (Houndsmills: Palgrave, 2011)CrossRefGoogle Scholar, for an extensive discussion of these issues.

⁴ The distinction between micro and macro is one of the most difficult ones in (the philosophy of) the social sciences. The distinction itself needs to be differentiated regarding ontological, meta-theoretical, and methodological aspects that are interrelated. We see this distinction to be an important one, yet treat it in a rather minimalist sense as basically saying that there exists social emergence, according to which some social phenomena and structures cannot be fully accounted for through the addition of, or interaction between, micro-level phenomena (that is, individual actions, speech acts, etc.). See Greve, Jens, Schnabel, Annette, and Schützeichel, Rainer (eds), Das Mikro-Makro-Modell der soziologischen Erklärung: Zur Ontologie, Methodologie und Metatheorie eine Forschngsprogramms (Wiesbaden: VS-Verlag, 2008)Google Scholar.

⁵ We want to re-emphasise the point about ontology again, as it was repeatedly raised by one of the reviewers of this piece, who objects to our objection against the prominence of the use of the concept of ontology in IR. The reviewer observes that it is hardly conceivable to proceed with any kind of study without some presuppositions of what is being studied, and that such presuppositions must not imply, for example, strong assumptions about a reality ‘out there’. We fully agree with the part on the presuppositions. Such presuppositions always need to be made as operative assumptions on the basis of specific distinctions. However, we still would argue that one of the main advances in the social sciences lies in moving from assumptions about being towards operative observations about how meaning is processed (and this acknowledges that ontology does not need to make strong assumptions about reality, but per definitionem it is about ‘being’).

⁶ ‘In other words, it [ontology; the authors] is a very specific form for taking the observer into account and placing him in the world. It simplifies descriptions of the world and society, in keeping with the realities of premodern society. One can assume that there is a reality continuum of world (and society) in which everything that is tales the form of a being [Seiendes], or, to be more precise, the form of a (visible or invisible) thing [res].’ See Luhmann, Niklas, Theory of Society, Volume II (Stanford, CA: Stanford University Press 2013), p. 192 Google Scholar; the entire subchapter on ‘The Semantics of Old Europe, 1: Ontology’, on pp. 183–96 of that book is probably the most concise treatment of the historical social function of ontology as a philosophical concept.

⁷ Jackson, Patrick Thaddeus and Nexon, Daniel H., ‘International theory in a post-paradigmatic era: From substantive wagers to scientific ontologies’, European Journal of International Relations, 19:3 (2013), p. 550 Google Scholar.

⁸ There is of course the oddity here of the word ‘international’. The more accurate term would be ‘interstate’, which is a relatively uncommon usage. ‘International’, strictly speaking, is almost a nonsense term. The correlation between states and nations is poor, there being only a couple of hundred states, and several thousand nations. By themselves, nations generally have little in the way of actor quality, and do not relate to each other in actor-like modes. There are some things that might count as ‘international’ relations in this literal sense, such as focused fear/hatred (for example, between Chinese and Japanese, and Albanians and Serbs or in earlier times French and Germans), or shared identity (for example, among the nations of the Anglosphere, or the Arab world). But these things are only a small part of what ‘international’ is taken to mean.

⁹ Perhaps the most developed example of this way of thinking is Niklas Luhmann’s Modern Systems Theory, in which society is conceived in terms of communicative function systems that are strictly separated from each other by defining conceptual dyads (for example, legal-illegal for law, true-false for science; powerful-non powerful for politics, having-not having monetary value for economics etc.; see Stichweh, Rudolf, ‘The history and systematics of functional differentiation in sociology’, in Mathias Albert, Barry Buzan, and Michael Zürn (eds), Bringing Sociology to International Relations: World Politics as Differentiation Theory (Cambridge: Cambridge University Press, 2013), pp. 50–70 Google Scholar, for an enumeration of function systems). Although function systems are defined by these dyads, they nonetheless share environments and make impacts on each other. Outside of the social world, and the social sciences, ‘functional differentiation’ is a concept frequently used in cell biology in relation to the study of the evolution of different kinds of cells. While this is more than a mere similarity in name given some of the earlier conceptions of functional differentiation in classical Sociology (ibid.), and while quite plausibly the concept can be applied to parts of living matter beyond the level of cells, it would be stretching the concept of functional differentiation in any of its established uses too far if one applied it to nature in its entirety, only to argue that the division between different natural sciences mirrors a functional differentiation of nature in the same sense that the social sciences mirror a functional differentiation of society. However, one could plausibly say that between the natural sciences there is a historically grown division of labor between different disciplines; that however this kind of functional differentiation within the system of science is also increasingly challenged in cross-disciplinary exercises from biochemistry to different kinds of quantum approaches.

¹⁰ Such a, mostly functional, differentiation within the system of science does not necessarily entail, as one reviewer of this piece argued, an ever-increasing complexity of the organisation of scientific knowledge and hence increasing complexity in this respect. Although empirically this seems to be the case, functional differentiation first and foremost means transformations of complexity (with reductions of complexity here leading to new complexity there), meaning that while new specialised subdisciplines or fields of study appear all the time, others disappear as well.

¹¹ Buzan, Barry and Little, Richard, ‘Why International Relations has failed as an intellectual project and what to do about it’, Millennium: Journal of International Studies, 30:1 (2001), pp. 19–39 Google Scholar.

¹² See, for example, Mitzen, Jennifer, Power in Concert: The Nineteenth-Century Origins of Global Governance (Chicago: University of Chicago Press, 2013)CrossRefGoogle Scholar; Buzan, Barry and Lawson, George, The Global Transformation: History, Modernity, and the Making of International Relations (Cambridge: Cambridge University Press, 2015)Google Scholar; Albert, Mathias, A Theory of World Politics (Cambridge: Cambridge University Press, 2016)Google Scholar.

¹³ Bayly, Cf. C. A., The Birth of the Modern World, 1780–1914: Global Connections and Comparisons (Oxford: Blackwell, 2004)Google Scholar; Osterhammel, Jürgen, The Transformation of the World: A Global History of the Nineteenth Century (Princeton, NJ: Princeton University Press, 2014)Google Scholar.

¹⁴ Buzan, Barry, From International to World Society (Cambridge: Cambridge University Press, 2004), p. 15 Google Scholar.

¹⁵ Debates about the question of whether IR is a discipline mostly are normative about whether it should be (seen as, organised as, etc.) as a discipline. See, for example, the recent discussion on the identity of IR in Turton, Félix Grenier, H. L., and Beaulieu-Brossard, Philippe, ‘The struggle over the identity of IR: What is at stake in the disciplinary debate within and beyond academia?’, International Relations, 29:2 (2015), pp. 242–244 Google Scholar. Our starting point on that matter is quite simply institutional-empirical: if now, and already for quite some time, a quite significant number of people treat IR as a discipline, prepare publications as if it was, organise conferences, professional organisations, and university departments as if it was, and find monthly salaries in their bank accounts paid on the assumption that it is, then for the time being it seems fair to treat it as such. The present contribution is a contribution to the debate on whether what is actually should be a discipline in that it probes one possible good reason for this, namely the existence of a distinct realm in the social world best studied by a discipline for IR.

¹⁶ Rosenberg, Justin, ‘International Relations in the prison of political science’, International Relations, 30:2 (2016), p. 6 Google Scholar.

¹⁷ See, among many others, Holsti, K. J., The Dividing Discipline: Hegemony and Diversity in International Theory (London: Allen & Unwin, 1985)Google Scholar, or succinctly in a recent interview, Onuf in Peer Schouten, ‘Theory talk #70: Nicholas Onuf on the evolution of social constructivism, turns in IR, and a discipline of our making’, Theory Talks (2011), available at: {http://www.theory-talks.org/2015/07/theory-talk-70.html} accessed 15 May 2017.

¹⁸ See, most notably, Gieryn, Thomas F., Cultural Boundaries of Science: Credibility on the Line (Chicago: University of Chicago Press, 1999)Google Scholar.

¹⁹ This being the title of the first study meeting of the International Studies Conference 11th Session held in Prague in March 1938, and documented in Zimmern, Alfred (ed.), University Teaching of International Relations (Paris: International Institute of Intellectual Co-operation, 1939)Google Scholar.

²⁰ Alfred Zimmern, ‘Introductory report to the discussions in 1935, in Zimmern, University Teaching, pp. 6–15.

²¹ See, for example, Chapter Five on ‘The Coordination of Disciplines’, pp. 167–70 in Ware, Edith E. (ed.), The Study of International Relations in the United States. Survey for 1934 (New York: Columbia University Press, 1934)Google Scholar.

²² Rosenberg, ‘International Relations in the prison’.

²³ See notably Holsti, The Dividing Discipline: Hegemony and Diversity in International Theory, and Schmidt, Brian C., The Political Discourse of Anarchy: A Disciplinary History of International Relations (Albany, NY: State University of New York Press, 1998)Google Scholar.

The disciplinary histories of IR vary according to the intensity in which they portray thinking about International Relations in the context of a long-standing history of ideas. The most intensive and voluminous treatment of the development in this regard to our knowledge remains the unpublished three-volume ‘Habilitationsschrift’ of Reinhard Meyers from 1986 (available only as manuscript through Bonn University library; Meyers, Reinhard, Paradigmata der internationalen Gesellschaft: Perspektiven einer Theoriegeschichte Internationaler Beziehungen, 3 vols (Bonn: Rheinische Friedrich-Wilhelms-Universität, Habilitationsschrift, 1986)Google Scholar.

²⁴ Wright, Quincy, The Study of International Relations (New York: Appleton-Century-Crofts, 1955)Google Scholar.

²⁵ Ibid.

²⁶ Ibid.

²⁷ Ibid., p. 36.

²⁸ See ibid., pp. 52–4.

²⁹ Ibid., p. 59.

³⁰ Albert, Mathias and Buzan, Barry, ‘International Relations theory and the “social whole”: Encounters and gaps between IR and Sociology’, International Political Sociology, 7:2 (2013), pp. 117–135 CrossRefGoogle Scholar.

³¹ Niklas, Luhmann, ‘“Was ist der Fall?” und “Was steckt dahinter?” Die zwei Soziologien und die Gesellschaftstheorie’, Zeitschrift für Soziologie, 22:4 (1993), pp. 245–260 Google Scholar. With the ‘anything goes’ Luhmann explicitly refers to Feyerabend’s Against Method: Feyerabend, Paul, Against Method: Outline of an Anarchist Theory of Knowledge (London: New Left Books, 1975)Google Scholar.

³² Wight, Martin, ‘Why is there no international theory?’, in Herbert Butterfield and Martin Wight (eds), Diplomatic Investigations: Essays in the Theory of International Politics (London: Allen and Unwin, 1966), pp. 1–33 Google Scholar; Walker, R. J. B., Inside/Outside: International Relations as Political Theory (Cambridge: Cambridge University Press, 1993)Google Scholar.

³³ Rosenberg, Justin, ‘The international imagination: IR theory and “classical social analysis”’, Millennium: Journal of International Studies, 23:1 (1994), pp. 85–108 CrossRefGoogle Scholar; Rosenberg, Justin, ‘Problems in the theory of uneven and combined development, Part II: Unevenness and multiplicity’, Cambridge Review of International Affairs, 23:1 (2010), pp. 165–189 CrossRefGoogle Scholar; Rosenberg, Justin, ‘Kenneth Waltz and Leon Trotsky: Anarchy in the mirror of uneven and combined development’, International Politics, 50:2 (2013), pp. 183–230 Google Scholar; Rosenberg, Justin, ‘The “philosophical premises” of uneven and combined development’, Review of International Studies, 39:3 (2013), pp. 560–597 Google Scholar.

³⁴ Rosenberg, ‘International relations in the prison’, pp. 11–15.

³⁵ Waltz, K. N., Theory of International Politics (Reading, MA: Addison-Wesley, 1979)Google Scholar; Rosenberg, ‘The “philosophical premises” of uneven and combined development’, pp. 193–201.

³⁶ Buzan, Barry and Lawson, George, The Global Transformation: History, Modernity, and the Making of International Relations (Cambridge: Cambridge University Press, 2015)Google Scholar.

³⁷ Trotsky, Leon, The History of the Russian Revolution (London: Pluto, 1997 [orig. pub. 1932]), p. 27 Google Scholar.

³⁸ We have argued earlier (Albert and Buzan, ‘International relations theory and the “social whole”: encounters and gaps between IR and Sociology’) that most IR theory makes at least implicit assumptions about what that wider social realm as a ‘social whole’ is. Spelling out these assumptions invariably would be a first step to then ask how within it the subject matter of IR is distinguished.

³⁹ Rosenberg, ‘International relations in the prison’. It would be possible to argue whether Rosenberg’s and Albert’s approach indeed belong to the same category in this context. For the time being, we have decided to leave them together: Rosenberg sees the international as a ‘dimension’ of social reality, Albert sees world politics as a (communicatively constituted) social system. Both delineate a realm from its relation to, and distinction from, a social environment (through either some kind of ‘dimensionality’ or through a system/environment distinction), so for the purposes of this article seem to belong into the same batch.

⁴⁰ See Waltz, Theory of International Politics, pp. 88–93.

⁴¹ It is an entirely different matter that many contributions who claim to be ‘only’ about perspective proceed actually on the assumption that the perspective in question mirrors the most relevant ways in which social reality is structured; see Albert, Mathias and Buzan, Barry, ‘Securitization, sectors, and functional differentiation’, Security Dialogue, 42/4–5 (2011), pp. 413–425 Google Scholar. See also the instructive discussion on ‘levels’ by Onuf in this regard: Onuf, Nicholas, ‘Levels’, European Journal of International Relations, 1:1 (1995), pp. 35–58 CrossRefGoogle Scholar. We have elaborated our position in relation to Onuf’s in Albert and Buzan, ‘International relations theory and the “social whole”’.

⁴² A ‘structural level’ does not even necessarily pertain to ‘macro’-structures alone, as, for example, singular ‘world events’ or ‘global microstructures’ can have structural effects on a global scale as well; see, for example, Knorr-Cetina, Karin, ‘Complex global microstructures: the new terrorist societies’, Theory, Culture & Society, 22:1 (2005), pp. 213–234 Google Scholar.

⁴³ And it is in this sense that ‘macro’ is not a property of the social world, but a contingent result of social evolution. See on this: Brunkhorst, Hauke, Critical Theory of Legal Revolutions: Evolutionary Perspectives (New York: Bloomsbury Academic, 2014)Google Scholar.

⁴⁴ Which means that ‘large and big’ might have a tendency to be ‘global’ as well, but this is not necessarily so and arguably significant structures existent in one world region only would also count.

⁴⁵ And beyond; see the lively debates on this issue in Wight, Colin, Dunne, Tim, and Hansen, Lene (eds), ‘The end of International Relations theory?’, European Journal of International Relations, 19:3 (Special Issue) (2013)Google Scholar.

⁴⁶ We are talking here about most relevant environment in the sense of being constitutive of a system/environment-distinction that is required to identify a system in the first place, that is, the environment of a system – of course, there are always myriads of other systems in a system’s environment.

⁴⁷ This is, in effect, saying that the present contribution could be seen as a late addition to that debate, however one that starts out by saying that there is no end in sight and seeks to identify promising pathways into what necessarily always remains unchartered terrain.