2.1.2. Multidimensional Proximity

Seeking to relate spatial analysis with the analysis of international relations to address these questions is particularly complex. Similar to geographical research, many international relations issues also emphasize the importance of multidimensional factors analysis, such as the understanding of history, geography, politics, economy, diplomacy, and factors related to religion [49]. The essence of TWC is the concrete manifestation of the relationship between countries in a specific practical activity. The production and deepening of this activity are bound to be affected by the comprehensive influence of political, economic, and cultural relations between countries. Therefore, it is feasible to apply the multidimensional perspective of geographical research [50] to the study of TWC relations, which has practical significance for crossing the current paradigm barriers in this field and making up for the lack of a single analytical perspective.

Multidimensional proximity provides an effective research framework for this attempt. Proximity is a concept widely used in geography and regional science [51]. The perspective for observing proximity is usually divided into monadic and dyadic. Proximity at the monadic level refers to the spatial proximity or coverage of a region, which emphasizes a phenomenon of spatial agglomeration. Proximity at the dyadic level focuses on the proximity between two regions or individuals, which emphasizes the distance (or differences and similarities) between two interactive regions or individuals. The latter is more commonly discussed in academic research. Proximity initially only refers to geographical proximity, that is, the distance between things [52]. It is generally considered to come from the observation of industrial agglomeration and knowledge spillover by economic geographers [53]. The spatial agglomeration of innovation activities makes people first realize the importance of geographical proximity to innovation. There is a substantial body of work on the relationship between geography and innovation, which explains that close geographical distance between actors is more conducive to face-to-face communication and interaction [54–56]. Additionally, frequent exchanges help to create a good cooperative relationship between actors, thereby enhancing the circulation of tacit knowledge and the production of innovative activities [57].

As research progressed further, scholars found that single geographic proximity could not fully explain the generation of innovation. Therefore, the multidimensionality of the research perspective has received attention and discussion. The French school of proximity proposed that proximity should include multiple dimensions, and suggests that proximity in other dimensions also had an important impact on the research object [58]. In addition to physical proximity, socioeconomic interdependence should also be considered [51]. Boschma systematically defined the concepts of cognitive and organizational, while language, and cultural proximity were also widely mentioned by other researchers [59–62]. What these dimensions have in common is that being proximate in any of them enhances coordination and reduces uncertainty, thereby contributing to knowledge production and innovation [53,60].

The flourishing of the theory of multidimensional proximity has resonated with other disciplines and broken through its early spatial scale perspective that focused only on local activities. On the one hand, a major research direction focuses on the geographical constraints of network formation and its evolution. This approach is based on the findings that geographic proximity tends to facilitate the formation of networks, which increases social contact, information exchange, and the creation of social relationships [57]. This also influences some scholars to classify these explanations as part of the geographical theories of networks [63]. Furthermore, criticism of the early concept of localized networks pointed out that such networks may not bring the expected effects of innovation, and "spatial myopia" or "lock-in" would reduce the explanation of localized networks [60,64,65]. In contrast, global relations based on economic globalization and the adjustment of production relations revealed that this theory can be applied to a wider range of spatial scale studies, such as global production networks or global value chains [66,67]. On the other hand, multidimensional proximity is recognized in other disciplines or studies that emphasize relational and geographical perspectives, and one of the important areas is international relations. Using geopolitics as a link, some scholars have provided linkages between the disciplines of political science and geography through the integration of international relations and political geography [68]. For example, Harvey Starr [68] advocated proximity in his research on international conflict, emphasizing the importance of geography, distance, and spatiality in theoretical and empirical work on international relations. Some scholars have also pointed out that proximity is a strong factor in predicting dyadic conflict, and the greater the "distance" between states, the greater the probability of conflict [69]. Although multidimensional proximity has been applied in many research fields, for transboundary water cooperation, there is still a lack of discussion on its generative mechanism from this perspective.
