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Bringing Morgenthau’s ethics in: pluralism, incommensurability and the turn from fragmentation to dialogue in IR

Why did IR pluralism end with so many incommensurable camps? (How) can IR be demarcated as a discipline where these camps can find common ground for dialogue without glossing over theoretical pluralism? To answer the first question, the paper argues that Morgenthau’s critique of IR as social science can explain the proliferation of camps in IR pluralism that are incommensurable and cannot engage in dialogue. By transcending the dilemma of politics as highlighted in Morgenthau’s critique of social science, theories today are ideological camps that bestow on morality an ideological function that justifies their powers-that-be that serve particular means/ends hierarchies. This leads to the proliferation of empirical causal analyses that cannot be debated, since they rely on political interests that theory ideologically justifies and offers internal validation. To avoid this problem, the paper answers the second question by proposing to demarcate the discipline through Morgenthau’s concept of ‘interest defined as power’. It argues that demarcating the discipline on the basis of this concept opens room for engaging in dialogue in IR through leaving open the normative debate of means and ends, and thus acts as a bulwark against the proliferation of ideological camps, while promoting theoretical pluralism.


Introduction
There is no one agreed definition of pluralism in International Relations (IR). Pluralism in IR may mean to 'deprive any particular methodology of the ability to claim a uniquely scientific status' (Jackson, 2011: 189 emphasis in original). It may mean promoting a project of a 'Global IR' that is no more dominated by one region or set of (state-based) actors (Acharya, 2014). It may mean 'expanding the methodological toolkit' a la analytic eclecticism (Sil and Katzenstein, 2008), questioning the dominance of neo-positivist methodology and its delegitimation of other approaches to knowledge production (Tickner, 2016), or, alternatively, a more open 'critical problem solving' approach (Brown, 2013). It may mean rejecting the 'evil' of isms, and in lieu focusing on 'midrange' theorising (Bennet, 2013;Lake, 2011), or, by contrast, theoretical exchange (Mearsheimer and Walt, 2013). Pluralism may mean avoiding the reproduction of IR as a colonial discipline that neglects important events in world history, such as the Haitian revolution (Grovogui, 2006), or tell the 'real story of Europe' altogether (Jones, 2006: 7). This is by no means an exhaustive list of what pluralism may mean, but enough to show that if 'isms' are authoritarian, divisive, evil, then the state of plural-ism reproduces these 'camps' further, with each camp 'relatively secure today, comfortable in the knowledge that it has a power based in the field' (Sylvester, 2013: 615).
The debate on pluralism in IR is inseparable from the question of what IR, as a discipline, entails and how it is demarcated as a discipline. The question 'what is IR' was thus recently debated in the journal International Relations, following Rosenberg's (2016) seminal paper that called for breaking the discipline out of the 'prison' of political science, and accounting for the independence of the 'international' and its implications for societal multiplicity. Rosenberg's critics immediately posited his failure to account for the prison of 'colonial modernity' in erasing multiplicity from IR (Blaney and Tickner, 2017a) and for failing to present a restrictive 'multiplicity' that is inclusive enough to 'encompass all the work that presently goes on in international studies' (Jackson, 2017: 83). Later critics raised similar concerns about Rosenberg's 'oddly Westphalian' conception of IR (Sears, 2018: 243), and suggested thinking about the multiplicity of 'social, natural and technological spheres' (Corry, 2018: 244), 'think[ing] of multiplicity and its consequences far beyond humanity' (Peltonen, 2018: 245), and 'deepening multiplicity' (Powel, 2018). What is evident here once again is the value of pluralism despite the lack of consensus on what it means, and consequently, what IR, as a discipline, may entail (Lake, 2016(Lake, : 1119. This background raises two questions that this paper engages with. First, why did IR pluralism end with so many incommensurable camps? Second, (how) can IR be demarcated as a discipline where these camps can find common ground for dialogue without glossing over theoretical pluralism? To answer the first question, this paper argues that Morgenthau's critique of IR as social science can explain the proliferation of camps in IR pluralism that are incommensurable and cannot engage in dialogue. A key problem with the IR pluralism debate is that political interests are used as entry points to theory but then legitimised through empirical validation and closed to normative scrutiny. In his critique of IR as social science, Morgenthau warned against this problem because it glosses over the dilemma of politics. This dilemma consists of the fact that, to paraphrase Cox (1981), in theory someone will always be a means and someone will always be an end. By glossing over this dilemma, theory bestows on morality the ideological function of justifying the power-that-be of a particular means/ends hierarchy. 1 This blurs the distinction between theory and ideology, on the one hand, and leads to the proliferation of empirical knowledge, which, having liberated itself from the dilemma of politics, in turn leads to the proliferation of ideologies that defend the status quo of particular powersthat-be, on the other. This explains why 'we have so many ideologies' that are incommensurable, 'and so few theories' in IR pluralism today (Morgenthau, 1959: 28). To avoid this problem, Morgenthau presented the concept of 'interest defined as power'. As a 'theory' of international politics, this concept puts intellectual order on IR as a discipline (Guilhot, 2011;Guzzini, 1998). An order that does not necessarily abolish pluralism, since there are various normative objectives that lead to the proliferation of theoretical approaches in IR, but that situates these theories in the broader theoretical framework of interest defined as power and in turn seeks to adjust those interests qua normative prioritisations of means and ends. Drawing on Morgenthau to answer the second question on demarcating the discipline and engaging in dialogue, this paper thus argues that Morgenthau's concept of interest defined as power is a useful analytical tool here. Specifically, it argues that demarcating the discipline on the basis of this concept opens room for engaging in dialogue in IR through leaving open the normative debate of means and ends, and thus acts as a bulwark against the proliferation of ideological camps, while promoting theoretical pluralism.
This paper is thus situated in the context of the pluralism debate in IR. More precisely, the paper is situated at the intersection between two sub-debates within pluralism in IR: first, the debate on fragmentation and end of IR, on which there was a recent special issue in the European Journal of International Relations (2013) and forum in International Relations (2017), and second in the debate on 'dialogue' in IR, on which special issues and forums were covered in Millennium (2011) andInternational Studies Review (2003). Drawing on Morgenthau, the theoretical contribution here is twofold: first, the paper illustrates the relevance of Morgenthau's critique of social science to the contemporary debate on pluralism in IR, particularly in explaining the issue of incommensurability. Second, the paper employs Morgenthau's concept of interest defined as power in a novel fashion to foster dialogue in a theoretically pluralist discipline. While the normative dimension in Morgenthau, particularly his critique of social science, was highlighted by intellectual historians (Frei, 2000;Guilhot, 2011;Petersen, 1999), and in various contexts (Karkour, 2018;Molloy, 2009;Roesch, 2014). And while the consequence of this critique was put forward to re-interpret the disciplinary history of IR (Williams, 2013), destabilise divisions between theoretical approaches (Behr and Roesch, 2012;Behr and Williams, 2017) and provide 'alternative theorising' to the meta-theoretical impasse in a fragmented discipline (Paipais, 2014: 355-356), this paper's unique contribution lies in drawing on Morgenthau's critique of social science to explain why theories become incommensurable ideologies, and, building on this, in offering a way forward for IR to be demarcated as a theoretically pluralist discipline where theories can find common ground for dialogue.
The argument develops as follows: first, the paper contextualises the problem of forgetting political interests in IR pluralism -that is, the problem of political interests being used as entry points to theory but then legitimised through empirical validation and closed to normative scrutiny. Second, the paper highlights Morgenthau's warning against this problem -that it omits the dilemma of politics -in his critique of IR as a social science. Third, the paper draws on this critique to explain the issues of incommensurability and dialogue in IR pluralism. Following this, the paper concludes by drawing the implications for dialogue in IR.

IR pluralism and the problem of forgetting
This section argues that the IR pluralism debate forgets the political interests upon which the various positions stand, and thus, forfeits the adjustment of the interests these stances represent. Political interests are used as entry points to theory but then legitimised through empirical validation and closed to normative scrutiny.
To avoid reducing legitimate knowledge production in IR to one methodology, Jackson (2011Jackson ( , 2017 proposes a pluralism in what constitutes as science. As Tickner argues, however, 'even if, following Jackson, one were to embrace a pluralist, post-foundational definition of 'science,' the core-periphery structure that is entrenched in Global IR (and, indeed, nearly all social science) would remain basically untouched ' (2013: 642). This critique echoes earlier reviews of Jackson's Conduct of Inquiry that problematised not only Jackson's typology of methodological pluralism (Humphreys, 2013;Wight, 2013), and omission of 'other-worldliness' (Acharya, 2011), but also his underplaying of the political interests that divide these 'methodologies', in favour of a liberal ethos of tolerance (Suganami, 2013). In other words, what distinguishes methodologies is neither logic nor reason, but political interests that Jackson simply forgot. These interests are then reduced to different methodologies that retain their scholarly legitimacy through their internal, empirical validation, obscuring thus the normative basis of 'science' (Reus-Smit, 2013).
The problem of forgetting is not specific to Jackson's Conduct of Inquiry. In fact, latest trends in the IR pluralism debate, such as Global IR and post-colonial IR, equally suffer from the problem of forgetting. Calls for pluralism as part of Global IR aim for a diverse and inclusive IR that gives voice to 'non-Western' actors Acharya and Buzan, 2019;Gelardi, 2019). 'Marked by a simultaneous increase in global and international connections and exchanges ' Katzenstein (2016: 153) argues, 'the dialogue of Global IR will serve the purpose of articulating and reinforcing rich diversities'. 'The idea of Global IR', says Acharya, 'serves as a framework for advancing IR toward a truly inclusive and universal discipline' (Acharya, 2016: 5). 'A challenge for Global IR', therefore, is 'how to build generalisable concepts and theories from a national or regional context that should not only be applicable to a specific country or region but must have broader generalisation potential' (Acharya, 2016: 6). But then here one may ask: who do these 'national' schools represent? In his critique of Acharya, Parmar (2019: 238) for example problematises the Global IR project where 'the true contributions of the West and non-West are recognised, synthesised, and celebrated . . . and yet one in which serious problems of class inequality persist'. In forgetting class interests, Parmar's critique highlights the particular, elitist, interests the various 'national schools' in Global IR represent.
A corollary to Parmar's critique here is the question whether 'national' experiences in Global IR can be essentialised. Bilgin (2008: 6), for example, argues that 'Western' and 'non-Western' experiences as well as their various interpretations have, over the years, clashed and fused in so many ways that 'non-Western' ways of thinking about and doing world politics are not always devoid of 'Western' concepts and theories'. The central issue, however, which Bilgin does not address, is do these 'fused' and complex 'West' and 'non-West' even have agreed representatives? In the absence of a consensus of representatives of civilisations, a dialogue of civilisations ends up silencing voices. 'For example' Petito says, the already-mentioned initiatives of Mediterranean regionalisation involving European and Arab countries are to be encouraged as a way of fostering bridges of communication and mutual understanding between the European Union and the Arab League; they can also constitute laboratories for the praxis of inter-civilisational dialogue. (2016: 87) But the Arab League does not represent 'Arab culture', only state representatives, largely, if not all, autocrats who suppress their people. Where is the 'civilisational dialogue' here? The problem with the dialogue Petito advocates is that 'traditions' that underlie 'non-Western' theories are in effect the result of political interests in more than one sense: as representatives with political interests but also as representatives competing to legitimise these interests among others within each tradition. The result is that any such 'non-Western' theory would prioritise those who speak in the name of tradition, or the 'local' (Gelardi, 2019), and giving the back seat to those who hold no such privilege. The 'representatives' of national schools, 'traditions', 'perspectives', thus risk becoming the shadows of neorealist and neoliberal schools in the previous US experience: silencing voices, restricting IR, representing exclusionary and unadjusted political interests, escaping 'Eurocentrism' to introduce 'Globacentrism'. This 'Globacentrism' is characterised by its forgetfulness of the political interests upon which the proliferated 'representatives', 'traditions', 'perspectives' stand, and thus, the forfeit of the adjustment of the interests these stances represent. Thus, the political interests of the representatives of 'non-Western traditions' or the 'local', once used as an entry point to theory, are closed to normative scrutiny. Rather, they are pushed under theory, depoliticised, legitimised through empirical validation and immune from normative critique.
Post-colonial scholars define pluralism in terms of 'decolonising' IR. Decolonising IR is not just about 'adding voices', says Capan, 'it is not only through "adding" more critical perspectives that coloniality can be challenged but through altering the practices of said knowledge production' (Capan, 2017: 6). Thus 'the intellectuals must firstly "decolonise their minds" and rethink the academic spaces and knowledges that they inhabit and reproduce . . . it is not enough to bring in new narratives or ways of conceptualising the field, but rather the binaries and dualities upon which coloniality is premised need to be overcome' (Capan, 2017: 7-8; see also Blaney and Tickner, 2017b;Fonseca, 2019;Holden, 2014;Sabaratnam, 2011;Zondi, 2018).
Here the key contribution consists of problematising the knowledge / power relationship in Western IR and post-Western IR. Thus 'decolonising IR' means exploring 'worlding beyond the West' (Holding, 2014), seeking 'alternative cosmologies' (Blaney and Tickner, 2017b), and going beyond 'epistemic imperialism' (Zondi, 2018). Yet, once again, post-colonialism essentialises the non-West. 'The radical cultural relativism that such views promote as the cornerstone of pluralism and openness' as Rosa Vasilaki forcefully argues, is perhaps the strongest version of essentialism -the one that reaffirms stereotypes like the West as change and the Rest as stasis, Europe as modernity and the 'global South' as tradition, the Westerner as secular and the 'Other' as religious and so on -and ultimately shares the fundamentalist view that when cultures mix, a violent act against their essence is taking place. (2012: 20) Consequently, there is not only an unproblematised acceptance of this newly established binary, but of turning it into a political project whose interests are simply forgotten and hardly open to normative scrutiny. As with the Global IR project, therefore, the political interests of the representatives of the 'rest', 'global South', 'other', once used as an entry point to theory, are closed to normative scrutiny. Rather, normative questions are reduced to the closure of the empirical justification that theory provides within itself, relying on the grounds of the 'culture', 'tradition', etc. -whatever the theorist herself finds as a legitimating tool.
In sum, latest trends on pluralism in IR suffer from the problem of forgetting, that is, they represent political interests but then forget these interests and forfeit their adjustment. Consequently, political interests, once used as an entry point to theory, are closed to normative scrutiny. Morgenthau warned against this problem in his critique of IR as social science because it glosses over the dilemma of politics central to IR and sought to restate the political as the adjustment of interests through his concept of 'interest defined as power'. It is therefore to this critique that the next section turns.

Morgenthau's critique of IR as a social science
Why is Morgenthau the suitable candidate for our analysis here? First, because he was the major opponent of IR as a social science in the history of the discipline (Guilhot, 2011;Williams, 2013). Despite Morgenthau's opposition to IR as a social science, his work has not only been misappropriated as positivist or summarised under realism, but also targeted by post-colonial critics (e.g. Hobson, 2012; see also Berenskötter, 2018: 815) for a Eurocentrism that Global IR is seeking to move beyond. Indeed, is not the problem that IR is a 'colonial discipline' with 'colonial origins' where Morgenthau belongs? (Capan, 2017). Morgenthau's work however does not fit into the definition(s) of 'Eurocentrism' in the discipline i.e. 'a hegemonic representation and mode of knowing that claims universality for itself' (Escobar, 2004: 217). To Morgenthau, there is no such thing as universality or universal history to begin with. There are rather limits to modernity, and therefore limits of 'modernity/coloniality' as knowledge (Capan, 2017). If the critique of Eurocentrism is also a critique of modernity, rationalism and positivism associated with American IR, to associate this IR with Morgenthau is a mistake. For Morgenthau's career, from Scientific Man (1946) onwards, consists of a critique of positivism, modernity and rationalism. It is precisely because little has been covered on this critique by Morgenthau until the end of the Cold War, that a largely caricatured understanding of his realism developed as a part of a 'Western' or 'American' IR (Behr and Heath, 2009), despite the fact that Morgenthau's intellectual influences were largely German speaking, for example Freud (Schuett, 2010), Nietzsche (Frei, 2000) and Weber (Turner and Mazur, 2009). As Hamati-Ataya (2010: 1087 emphasis in original) in an earlier work on Morgenthau argues, 'Morgenthau's approach is successful in identifying Realism's reflexive challengebecause it acknowledges its political nature and its relevance to scholarship'.
The second reason Morgenthau is a suitable candidate is because he does not only share a post-Nietzschean, epistemological starting point with post-colonialism, but also goes beyond the latter in refusing to close normative scrutiny within the political. If decolonisation, going beyond 'Eurocentrism', is about decolonising the mind from binary thinking and identity formation (Capan, 2017), Morgenthau is an appropriate candidate to provide this critique, for he similarly critiqued Schmitt for the friend/enemy binary (Roesch, 2014) as well as the Cartesian dualities (Behr, 2013). Thus, post-colonialism and Morgenthau's classical realism share the same epistemological starting point: post-Nietzschean perspectivism (Vasilaki, 2012: 5). Indeed, post-colonialism, in its most radical post-structuralist critique of knowledge/power returns to the basic questions Morgenthau was grappling with in the post-Nietzschean age: 'where to go after the provincialisation of Europe, after the realisation that power and knowledge are mutually constitutive and after 'objectivity' has been proven both false and undesirable' (Vasilaki, 2012: 20). In both cases, there is an acknowledgement of the limits of universalisation of theory, yet in Morgenthau there is also a refusal to close normative scrutiny within the political (Paipais, 2014).
What is, then, Morgenthau's critique of IR as a social science?

Morgenthau and the critique of IR as a social science
Morgenthau's critique of IR as a social science is two-fold. First, it is a critique of theory transcending the dilemma of politics and becoming ideology. Second, it is a critique of the proliferation of empirical knowledge, which, having liberated itself from the dilemma of politics, in turn leads to the proliferation of ideologies that defend the status quo of particular powers-that-be. In an important, albeit neglected, passage Morgenthau defines the dilemma of politics as follows: . . . the totality of human actions presents itself as a hierarchy of actions each of which is the end of the preceding and a means for the following. This hierarchy culminates in the ultimate goal of all human activity which is identical with the absolute good, be it God, humanity, the state, or the individual himself. This is the only end that is nothing but end and hence does not serve as a means to a further end . . . In the last analysis, then, the doctrine that the ethical end justifies unethical means, leads to the negation of absolute ethical judgments altogether. For if the ethical end justifies unethical means, the ultimate and absolute good which all human activity serves as means to an end justifies all human actions. (Morgenthau, 1945: 9) The dilemma here lies in the choice of political end, which by necessity leads to the exclusion of all other ends and reduces them to 'means'. Due to this process of exclusion, necessary choice leads to the impossibility of 'ethical judgments altogether'. This, according to Morgenthau, leads to a basic contradiction between morality and power in matters political. But the mere presence of this contradiction does not mean that political actors surrender to the impossibility of ethical action. Rather, 'the contradiction between the political act and morality and the logic of the power relation itself compel the political actor to make it appear as though his striving for power and the exercise of it, far from violating morality, were actually its consummation' (Morgenthau, 1962a: 13). In other words, the political actor engages in a process of self-deception where they portray to themselves that an act of power is in fact an act of morality. Following this, Morgenthau argues, 'the political actor now can proceed with a good conscience, being assured of his moral superiority and the moral inferiority of the object of his power' (Morgenthau, 1962a: 13).
The function of morality in this context is ideological: it conceals power from itself and the actor. In turn, it conceals that the truth about social science is the truth about the dilemma of means and ends. 'That concealment, that elaborate and subtle and purposeful misunderstanding of the nature of political man and of political society, is one of the cornerstones upon which all societies are founded' (Morgenthau, 1958: 28). But while society confuses power for morality, and thus employs morality to play an ideological function, the role of a theory of international politics is to reveal this 'ideological veil', that is, remind power that it is power, and not morality. It must remind power that it appears 'as something other than what it actually is' and that 'deception -deception of others and of self -is inseparable from the exercise of power' (Morgenthau, 1970: 14). In other words, the role of theory here is to tell society that its morality provides an ideological cover for power, that is to say, that it confuses power for morality. The theorist in this endeavour faces two limitations: the limitation of origin, which determines the perspective from which he looks at society, and the limitation of purpose, which makes him wish to remain a member in good standing of that society or even to play a leading role in it. (Morgenthau, 1959: 21) These challenges cannot be completely met, since the perspective's origin will always be socially and politically situated, and the theorist depends on society for their survival and reputation: It stands to reason that political science as a social institution could never hope even to approach this ideal of a completely disinterested commitment to the truth. For no social institution can completely transcend the limitations of its origin, nor can it endeavour to free itself completely from its commitment to the society of which it forms a part, without destroying itself in the attempt. (Morgenthau, 1959: 22) Despite this, Morgenthau argues the task of theory is to demonstrate awareness of the tension between power and morality, and be morally committed to the quest to truth: Yet while political science as a social institution cannot hope even to approach the ideal, it must be aware of its existence; and the awareness of its moral commitment to the truth must mitigate the limitations of origin as well as the compromises between the moral commitment and social convenience and ambition, both of which no political scientist can fully escape. (Morgenthau, 1959: 23) Political realism, therefore, as Morgenthau argues in his 'fourth principle' in Politics Among Nations, is unwilling to gloss over and obliterate that tension [between morality and power] and thus to obfuscate both the moral and the political issue by making it appear as though the stark facts of politics were morally more satisfying than they actually are, and the moral law less exacting than it actually is (Morgenthau, 1978: 10) The key in the quest for truth in matters political is to reveal (and restrain) the ideological function of morality vis-à-vis power (Morgenthau, 1959: 27). This quest is especially pressing and challenging in international politics since, 'the main function which morality performs today for international politics is ideological. It makes it appear as though the interests and policies of individual nations were the manifestations of universal moral principles' (Morgenthau, 1959: 28). That is to say, morality does not limit power, but justifies it. This blurs the distinction between morality and ideology and ideology and theory: 'The distinction between ideology and morality becomes blurred, and so becomes the distinction between ideology and theory' (Morgenthau, 1959: 28).
To maintain the distance between ideology and theory -that is, to render theory immune from the ideological function of morality, Morgenthau proposes his concept of 'interest defined as power' in a normative sense. Thus, by making power its central concept, a theory of politics does not presume that none but power relations control political action. What it must presume is the need for a central concept which allows the observer to distinguish the field of politics from other social spheres, to orient himself [and / or herself] in the maze of empirical phenomena which make up that field, and to establish a measure of rational order within it. (Morgenthau, 1958: 39) Theory 'presents a map of the political scene' and it is 'not limited to rational explanation' (Morgenthau, 1958: 40). Rather, 'a theory of politics also contains a normative element' (Morgenthau, 1958: 40). This normative element is to bring in morality not to ideologically justify power, but to restrain it (Lebow, 2011: 557-558). As Alexander Reichwein argues therefore, to Morgenthau 'political science in general, and any theory in particular was not only an instrument to explain politics, but also normative compass and an intellectual weapon' (Reichwein, 2016).
It is in this context that Morgenthau employs the concept of 'interests defined as power' to demarcate IR as a discipline. He presents it as a 'theory' of international politics, not to present one theory among others, but to put an intellectual order on IR as a discipline (Guilhot, 2011;Guzzini, 1998). This theory does not necessarily abolish pluralism, for there are diverse moral claims and normative objectives which lead to the proliferation of theoretical approaches in IR. As Morgenthau put it, 'hypothetically one can imagine as many theories of international relations as there are legitimate intellectual perspectives from which to approach the international scene' (Morgenthau, 1959: 16).
Morgenthau was also, as he wrote in his autobiography, aware of the problem of theoretical reductionism: the 'impossibility of accounting for complexities and varieties of political experience with the simplicities of a reductionist theory, economic [as with Marxism] or psychological [as with psychoanalysis]' (Morgenthau, 1977: 14). Morgenthau's 'interest defined as power' instead situates IR theories in a broader framework that seeks to adjust those interests qua normative prioritisations of means and ends. As Williams (2005: 169) argues, it is 'a rhetorical device that seeks to use the political power of this concept to encourage critical reflection and dialogue about interests and their relation to identity -to how a society sees itself and wishes to be seen by others'. Morgenthau's theory, thus as Guilhot argues, 'emerge[s] as a normative statement on what political science should be, not as a discourse of specialisation. . .. to delineate this territory and make it immune to the cues of behavioralism ' (2011: 129). In other words, Morgenthau's theory stands in juxtaposition to a value-free, liberal rationalist, empirically focused, discipline, devoid of the dilemma of politics. 'The focus of the theory, in the last instance, was its repudiation of a liberalism masquerading as value-free social science and rooted in the tradition of Enlightenment rationalism' (Guilhot, 2011: 132). This does not mean supporting value relativism, a 'utopia power', since Morgenthau critiques Schmitt and later Carr on this (Morgenthau, 1948;1958;1962b), but, rather, establishing the limits of what theory can achieve -that is to say, the limits of both social science and power (Behr, 2013). 'A theory of politics, to be theoretically valid, must build into its theoretical structure, as it were, those very qualifications which limit its theoretical validity and practical usefulness' (Morgenthau, 1959: 20). As Hom and Steele (2010: 292) argue therefore, 'classical realism's general theory of IR may be seen as a meta-argument against the possibility of a truly general theory'.
These limits include, especially, the policy oriented theory (e.g. see Wallace, 1996;Desch, 2015), of which Morgenthau was highly critical. For the closer this theory got to power, the less it became committed to truth, particularly in the context of Vietnam. 'Morgenthau's political agenda during the Vietnam War' as Molloy (2019: 16) lately argued in this journal, thus 'fulfils this most primary goal of a reflexive approach, i.e. a theorist's commitment to understanding his/her role within the context of the production of knowledge and the implications of that knowledge within the social and political realms'. Morgenthau's role as a reflexive scholar in Vietnam was to reveal the limits of power to the power-that-be, the US government. Revealing the limitations of power, however, according to Morgenthau, should not be specific to governments only -the same dynamic may also apply to any, official or unofficial, male or female, top or bottom, capital or labour, power. In exposing the limits of power, Morgenthau calls for exposing the limits of any power, of any social science, that purports to speak on behalf of any group. As Cozette (2008: 10) argues, 'by permanently reminding Power that it lies when it pretends to embody Truth or Justice, a realist theory is in essence a critical weapon turned against power'. Thus, pace Hamati-Ataya, perhaps the most outspoken reflexivist in IR, the 'problem of values' is not a problem that 'exists as such only for positivism' (Hamati-Ataya, 2011: 283; see also Sjoberg, 2015: 397). Rather, the possibility of 'collusion with power' (Hamati-Ataya, 2011: 279) extends beyond positivist research and highlights the significance of Morgenthau's proposition that politics is about 'interest defined as power'. For the literature Hamati-Ataya cites as exemplar of reflexivist IR, critical theory (e.g. Linklater, 1992), constructivism (e.g. Onuf, 1989;Kratochwil, 2002) and the English School (e.g. Dunne, 1998) have not been particularly immune from losing critical edge (e.g. see Jahn's 1998 critique of Linklater), and/or naturalising the political (Epstein's, 2013

critique of Onuf and Kratochwil).
Hamati-Ataya critiques Morgenthau's 'philosophical' approach that 'fails to unify its axiological and objectivist claims into a uniformly rigorous discourse on world affairs' (Hamati-Ataya, 2010: 1101. What is meant here by 'rigorous discourse'? If the meaning here is empirically verifiable statements a la positivism, then Morgenthau rejects such discourse because of the complexity of social planning (Morgenthau, 1944). Moreover, it is in this movement to 'rigour' that reflexivist IR loses its reflection and becomes forgetful of its political origins. This is not only clear above with the literature that Hamati-Ataya associates reflexivism (2011: 274), but also a more general critique raised against reflexivist research in IR that turns from 'a project based on recognising one's own limitations . . . into a claim to enlightenment' (Knafo, 2016: 44). Contra this scholarship, as Molloy argues in response to Hamati-Ataya, Morgenthau's realism is 'politically reflexive regarding scholarship and its relationship to power and the modes of knowledge production' (2019: 15 emphasis in original). Politically reflexive in that it is reflexive with a political agenda: a responsibility to challenge the power-that-be through invoking a normative concept of power as a bulwark against morality playing an ideological function of justifying, rather than exposing the limitations of, power (Behr and Roesch, 2012).
The necessity of Morgenthau's normative meaning of power lies in the political dilemma underlying IR or social science more generally. When IR as social science glosses over this dilemma, it does not only offer one normative judgment of the means and ends in the hierarchy of values, but also turns theory into an ideology that switches the function of morality from the restraint of power to the justification of a particular power-that-be. This leads to the proliferation of empirical, causal knowledge, which, having liberated itself from the dilemma of politics, proliferates political ideologies that protect the status quo of particular powers-that-be. This explains why to Morgenthau a focus on causality or causal analysis separated from the political dilemmas in action gives an inadequate concept of science. Indeed, in Science: Servant or Master, Morgenthau associates the latter conception of science with the ancient, immanent, Aristotelian, concept, which he juxtaposes with the modern concept: Aristotle was satisfied with the immanent meaning of science. Here science finds its meaning within itself, in the theoretical constitution of the human soul that aspires to knowledge for its own sake . . . Modern consciousness revolts against this indifference . . . We are no longer capable of that self-assurance, which appears naïve in retrospect, that salutes each new knowledge as a new victory carrying its justification within itself. (1972: 6-8) Morgenthau's critique of IR as a social science is thus that by transcending the dilemma of politics, it, firstly, turns theory into ideology. And secondly, it leads to the proliferation of empirical knowledge, internally validated and yet inadequate as it serves as the ideological justification of the status quo of particular powers-that-be. Morgenthau's 'realism is therefore', as Cozette argues, 'best described as a permanent critique of the powers-that-be that constantly challenges the status quo and the ideological apparatus upon which it rests ' (2008: 14). The significance of this Morgenthauian critique is that it helps illuminate the issues of incommensurability and dialogue in IR pluralism, to which the paper now turns.

Morgenthau, incommensurability and dialogue in IR pluralism
This section firstly argues that Morgenthau's critique of IR as social science can explain why IR theories today are incommensurable and cannot engage in dialogue. By transcending the dilemma of politics as highlighted by Morgenthau, theories today are ideological camps that bestow on morality an ideological function that justifies their powers-that-be that serve particular means/ends hierarchies. This leads to the proliferation of empirical causal analyses that cannot be debated, since they rely on these hierarchies that theory ideologically justifies and offers internal validation. Building on this, the section secondly argues that the central task to engage in dialogue without glossing over pluralism in IR is to start with the political in a Morgenthauian sense: to demarcate the discipline on the basis of the concept of interest defined in terms of power.
With notable exceptions (e.g. Wight, 1996), IR scholars often draw on Kuhn's definition of incommensurability (Hollis and Smith, 1990;Lapid, 1989;Monteiro and Ruby, 2009;Vasquez, 1997). This is problematic since the limitation in a social science does not only pertain to the inapplicability of the methods of natural science to social science. Rather, it is that many of the themes in the philosophy of science, such as Kuhn's 'incommensurability', change their meaning once they traverse the realm of the natural to the social. They add to the empirical problem the dilemma of politics. The addition of this dilemma in social science means that theoretical camps are chained on a springboard of means and ends that render theories 'incommensurable' in a sense that is different from Kuhn's (1970) understanding of the term. For it is the political positions that these theoretical arguments hold that make them exclusionary of one another. This means the question of incommensurability and its link to the fragmentation of the discipline is not simply one of diverse 'perspectives' (Wight, 1996), or 'methodologies' (Jackson, 2011). And nor does it simply lie in the 'complexity of society' per se (Dunne et al., 2013: 417;as critiqued in Jahn, 2017: 71), or a misunderstanding of epistemology (Wight, 2019). It is, rather, as Jahn argues, 'the modern episteme that endows the individual elements of such complex systems with their own internal nature and hence leads to fragmentation' (2017: 72). As with Morgenthau, however, the key here is not to surrender to a ubiquitous science that is merely justified through internal, empirical, validation.
The ubiquity of this science was highlighted in Kurki's analysis of causality (2006), which draws on Aristotle to highlight various causalities across the positivist-post-positivist spectrum. But IR as a discipline cannot justify each theoretical contribution in light of its empirical, causal validation. It cannot accept each new voice as a 'victory in itself' (Morgenthau, 1972: 6-8). Since then, the normative underpinnings of causal decisions are closed to scrutiny and each victory becomes part of an ideological camp that bestows on morality the ideological function of justifying the power-that-be of particular means/ends hierarchies. By concerning itself with 'scientific ontology' i.e. debate over theoretical explanation, rather than what explanation is (Nexon and Jackson, 2013), IR obscures the normative basis of 'science' (Reus-Smit, 2013), which entails the prioritisation of means and ends Morgenthau highlighted. Consequently, each 'victory' becomes part of an ideological camp, whose imposition of particular means/ends hierarchies as an act of power cannot be restrained by morality, but rather bestows on morality the ideological function of justifying such hierarchies. In this case, empirical causal analysis does not only proliferate, but it also cannot be debated, since it relies on normative hierarchies that theory ideologically justifies and offers empirical, causal validation. This does not, per se, indicate a 'healthy and dynamic discipline' (Jahn, 2017: 72), particularly when fragmentation may mean lack of normative dialogue between the various ideological 'camps' (Sylvester, 2013).
Of course not all scholars agree that the incommensurability of isms is intrinsic to the subject matter of politics. Lake (2011: 471), for example, finds the evil in the 'isms' themselves, that is, the 'pathologies' of grand theories, that can be escaped in mid-level theorising. This view is shared by those who call for more eclectic hypothesis testing (Sil and Katzenstein, 2008), more focus on concrete political problems (Kurki, 2011) and 'causal mechanisms' more generally (Bennett, 2013: 465). But these calls, as Jahn noted, 'rest on meta-theoretical commitments and methodological practices from which [they] receive [their] scientific status and validation' (Jahn, 2017: 69; see also Reus-Smit, 2013: 589;andNau's, 2011 critique of Lake, 2011). For example, the focus on causality and 'causal mechanisms' in eclectic and mid-range theory has been associated by some with scientific realism (Bennett, 2013), by others with neo-positivism (Jackson and Nexon, 2013). Once this commitment is taken as a given, there is a shift from theory to methods. One issue with such shift, as Mearsheimer and Walt (2013: 439) argued, is that different (meta)-theoretical perspectives might lead to different empirical conclusions. These conclusions are not simply based on different interpretations of causality, but are representative of political interests that are in turn linked to the meta-theoretical commitments (Suganami, 2013), which mid-range theory and analytical eclecticism take as a given. These political interests bestow on morality the ideological function of legitimising the normative hierarchies of the particular powers-that-be that mid-range theory and analytical eclecticism serve. This can be contrasted with 'grand theories', which as Felix Berenskötter argues, possess an 'ability to ground their ontologies, explanations and prescriptions in answers to philosophical questions of what drives 'us', where and who 'we' are, and should be, in space and time. As the answers can only ever be particular, they are also political' (Berenskötter, 2018: 833). Thus Berenskötter suggests 'deep theorising' as 'also a form of political theorising' (Berenskötter, 2018: 833). In this context, 'causality' cannot present the normative evaluation required of these 'deep theories', since causality itself is built on the choice of normative means and ends central to the political. The key task to engage in dialogue without glossing over pluralism in this context becomes to start with the political in a Morgenthauian sense: to demarcate the discipline on the basis of the concept of interest defined in terms of power and begin with a normative debate regarding means and ends.

Morgenthau's political and dialogue in IR pluralism
Calls for dialogue in IR are not new (Palmer, 1980: 361), and, like pluralism, dialogue has more than one meaning. Previous attempts to address the question of dialogue in IR presented 'via medias' and/or 'middle grounds'. Yet, remaining within the rationalist end of the methodological spectrum, these attempts were at best contentious, at worst feeding into the latter's exclusionary dominance in IR. As Steve Smith argued of mainstream constructivism for example: The main debates in the discipline for the next decade will be between rationalism and constructivism, but this is a little misleading because it implies that constructivism is positioned between the two approaches: I think that some of the most cited authors are not at all positioned between the two, but instead are really part of rationalism. (2002: 74; on 'mainstream' constructivist literature see Wendt, 1999;Adler, 1997;Checkel, 1998) Recent calls for dialogue in IR have thus been, rightly, suspicious of such attempts at 'grand theorising'. Dunne et al. (2013: 407) instead called for 'integrative pluralism', which 'allows for more diversity than 'unity through pluralism' and more interaction than 'dis-engaged pluralism'. 'Integrative pluralism', thus, 'is not an attempt to forge competing knowledge claims into one overarching position that subsumes them all. It is not a form of theoretical synthesis, nor is it a middle ground that eclectically claims to take the best of various theories to forge them into a 'grand theory of everything' (Dunne et al., 2013: 416). Rather, 'the ultimate test of integrative pluralism will be researchers from multiple perspectives engaging in the practice of pluralism through engagement with alternative positions where their concerns and research interests overlap' (Dunne et al., 2013: 417). Others, such as Hutchings, call for 'dissonance' and 'negotiation' as key ethical concepts for dialogue in 'pluriversality' (Hutchings, 2019: 122). Furthermore, calls to transcend the essentialism of the 'non-West', turn to dialogue via re-defining the universal in terms of egalitarian principles (Vasilaki, 2012: 21), and/or heterogeneity (Matin, 2011: 365).
These contributions raise an important question: on what basis can scholars 'engage' in dialogue or 'negotiate' an 'egalitarian' or 'non-hegemonic' universality here? Here the normative dimension is downgraded in the literature on dialogue in IR pluralism: there is no mention of political interests -instead, 'theoretical results' that need to be explicit (Dunne et al., 2013: 419). The success of 'negotiation . . . involves cultivating relational and creative resources for finding ways of working with others' (Hutchings, 2019: 122). Transcending the essentialising of the 'non-West' means drawing on theoretical schemes, such as 'uneven and combined development ' (e.g. as in Matin, 2011;later Rosenberg, 2016). But if theories are ideological camps, as highlighted with Morgenthau above, then making theoretical results explicit or being open to negotiation is not sufficient to engage in dialogue as part of a pluralist discipline. This is because theories remain internally validated, and given the omission of the dilemma of politics, they do not challenge but justify their powers-that-be that serve particular means/ends hierarchies. Therefore, as Jackson (2017) argued, theoretical schemes such as 'uneven and combined development' take IR 'out of one [ideological] prison, into another'.
Given this background, one cannot, like Jackson (2011), simply jump into 'dialogue' with a liberal ethos and expect it to perform the political task of accommodation. Pace Habermas, power cannot be substituted for the rationality of the 'better argument' (Mouffe, 1999: 749-750). And nor can dialogue mean 'reciprocal exchange for mutual learning' (Eun, 2018: 440), without first accounting how such learning can take place when the hierarchies of means and ends contradict, and mutually exclude, one another. For dialogue is an imprecise term, not only in the sense of what kind of dialogue are we having and the boundaries/rules of dialogue (Hutchings, 2011), but also what structural and ideological conditions are necessary as perquisite for dialogue. If dialogue is to retain its meaning in the Greek term dia-logos, which 'is best understood as an effort by two or more people to make something new together' (cited in Lapid, 2003: 130), therefore, the central task to avoid the 'evil of isms' is to start with the political in a Morgenthauian sense: to begin with a normative debate regarding means and ends, and thus, to 'raise the question of the meaning of knowledge itself and to answer it by searching not for knowledge of any kind, but for the knowledge that is worth knowing' (Morgenthau, 1972: 11).
Critics may object here: 'and who will decide' what 'knowledge' is 'worth knowing'? Should we not, given we have no answer to this question, then agree to keep 'IR' as broad/pluralist as possible? (e.g. see Jackson, 2017;Tickner, 2011;Dunne et al., 2013;Acharya, 2014). The problem with such objections is that despite their call for pluralism, they set their -often-liberal -normative boundaries to the science debate and do not open these boundaries to debate (Wolff and Zimmerman, 2016;Suganami, 2013). In other words, they themselves settle the normative debate before the discussion starts and thus close the discussion of normative justifications. An alternative approach here is for theory to be reflexive about the trade-offs involved in theory building -of the theory's means and ends. And secondly, for theory to be open to engage in a dialogue over these trade-offs. This way, theory can not only be reflexive and open to dialogue, but also pursue a normative concept of power a la Morgenthau, as opposed to an empirical concept of power a la Schmitt (Behr and Roesch, 2012). The benefit of this concept is that it opens room for engaging in dialogue in IR through leaving open the normative debate of means and ends, and thus acts as a bulwark against the proliferation of ideological camps, while promoting theoretical pluralism. The concluding section of the paper illustrates this benefit, by drawing the implications of the Morgenthau's critique of social science for dialogue in the context of the IR pluralism debate.

Conclusion: 'interest defined as power' for dialogue in IR pluralism
Morgenthau's scepticism about social science as the instrument of power-that-be has waned over the decades. As Michael Williams argued in his contribution to the 2013 special issue on the 'end of IR' in this journal: IR lost its previous skepticism toward social 'science' and became in many ways a standardbearer for precisely the kinds of political knowledge that [classical realists] had been at pains to reject and which they sought to construct the field of IR in opposition toward. Indeed, if one wished to be particularly provocative, it is possible to say that from this perspective, what is often taken as the defining moment in the invention of IR theory -the publication of Kenneth Waltz's Theory of International Politics -actually marked the culmination of a move away from the field's beginnings and represents the 'end' of IR theory as conceived by [classical realists]. (Williams, 2013: 657) Building on this, this paper drew on Morgenthau's critique of IR as a social science to argue that it can explain the proliferation of camps in IR that are incommensurable and cannot engage in dialogue. By transcending the dilemma of politics as highlighted by Morgenthau, theories today are ideological camps that bestow on morality an ideological function that justifies their powers-that-be that serve particular means/ends hierarchies. This leads to the proliferation of empirical causal analyses that cannot be debated, since they rely on political interests that theory ideologically justifies and offers internal validation. To avoid this problem, the paper proposed demarcating the discipline through Morgenthau's concept of 'interest defined as power'. This concept, the paper argued, opens room for engaging in dialogue in IR through leaving open the normative debate of means and ends, and thus acts as a bulwark against the proliferation of ideological camps, without glossing over theoretical pluralism. This raises the question: how can theory pursue a normative concept of power a la Morgenthau -a concept of power whose purpose is not to impose, but to mutually adjust the various interests in the political? To illustrate the benefit of this concept, the concluding section of the paper depicts its implications for dialogue by drawing on two examples from the IR pluralism literature cited at the outset.
The first example is Jackson's Conduct of Inquiry. In his reply to Jackson's Conduct of Inquiry, Suganami argues that the choice of different methodologies depends on the type of questions the researcher asks (2013: 268). Furthermore, Suganami argues that this choice is determined by 'politics'. This politics determines whether the researcher seeks (neo)positivist or analytical approaches to control the status quo, or, alternatively, to transform the status quo to a more emancipatory order with critical realism and reflexivism (Suganami, 2013: 268). The lesson this paper draws from Morgenthau here is that whatever the choice is, the intrusion of politics Suganami highlights means that the theorist has a responsibility to acknowledge the limitations of the power-that-be of both the status quo and the emancipatory order by allowing normative scrutiny to the ends and means of theory. For example, if the theorist seeks to control and predict within the parameters of the status quo (as with Waltz, 1979), it is crucial in this case not to remove the theorist qua decision-maker and justify this status quo through the 'rational' imperatives of some 'system level' abstraction (Bessner and Guilhot, 2015: 87-88). For this will allow foreign policy elites 'to define political rationality in their interest and to protect those interests as some objective raison d'état' (Behr and Heath, 2009: 345). And this means, as Behr and Heath (2009: 344-345) warned, that Morgenthau's realism will lose its original role as an ideology critique and (neo)-realism will end up ideologically justifying the foreign policy apparatus that serves some elite-based interest. To overcome this issue of theory becoming the ideology of the status quo, therefore, it is crucial to identify, firstly, who this status quo serves as an end and who is excluded as a means, and secondly, why this ends/means hierarchy is justified. The choice of means and ends can then open a dialogue with other theories that seek to overthrow this status quo for an order that produces new hierarchies of means and ends. It is noteworthy here that IR theorists, particularly post-positivists, already do this in their critique of other theories (especially positivists). For example, contra calls for a pluralist IR with 'policy relevance' (e.g. see Desch, 2015), feminists problematise the reduction of relevance to the realm of security narrowly defined in terms of the foreign policy elites as an end (e.g. Sjoberg, 2015; see also Voeten, 2015: 402). This critique should not only be applied to theories branded as 'elitist' or 'positivist' but to all theories, including the various strands in feminism. Once all theories are open to normative scrutiny in this same manner, a normative concept of power can then play its function to mutually adjust the various political interests the various hierarchies of means and ends represent, and, crucially, act as a bulwark against ideological camps without glossing over theoretical pluralism.
The second example from the literature cited at the outset of the paper is the Global IR project associated with Acharya and Buzan's works (e.g. Acharya, 2014;Acharya, 2018;Buzan, 2016). Here, calls to include Brasilian (Alejandro, 2019), Chinese (Zhang and Chang, 2016), Indian (Mallavarapu, 2009), Japanese (Watanabe, 2019) and Turkish (Çapan, 2016) schools in IR, cannot evade the question of who are the ends and means of these schools without being exclusionary (Parmar, 2019), and thus bestowing on morality what Morgenthau referred to as the ideological function of justifying power.
Here 'national schools of IR might [not only] become, or be seen to become, tools of government in the service of the national interest', as Buzan once raised his concern (2016: 157), but also have no bulwark against the ideological justification of such interest in case it purports to represent universal moral values. Thus, in the context of Global IR, Morgenthau's 'interest defined as power' stands as a bulwark against the danger of 'national schools' beyond the West 'trying to replicate the Western success of universalising their own history and political theory' (Buzan, 2018: 412). The normative meaning the concept of power holds here means to adjust the various interests between and within these schools (Behr and Roesch, 2012;Roesch, 2014). It means refusing to depoliticise theory's political stance, which leads to theory transcending the dilemma in politics, and thus turning into ideology. It means heeding to Morgenthau's warning in Politics Among Nations that 'all nations are tempted . . . to clothe their own particular aspirations and actions in moral purposes of the universe' and 'it is exactly the concept of interest defined in terms of power that saves us from both that moral excess and that political folly' (Morgenthau, 1978: 11). This warning is especially relevant today with the rise of excessive nationalism in world politics, and in particular in the East Asian context (Schweller, 2017). Morgenthau's lesson to the Global IR project therefore is not to attempt to universalise the particular (as Acharya advocates), but to put a check on the powers-that-be that these schools represent by opening to normative scrutiny the means and ends of their ethical hierarchies within as well as between nations.

Disclosure
Dominik Giese has received funding from the European Union's Horizon 2020 Research and Innovation programme under the Marie Sklodowska-Curie Grant Agreement No 722826.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.