This chapter critiques the dualist limitations of Hegelian dialectics in International Relations, which organise subject–object relations through oppositional or complementary logics and thereby reproduce geocentric essentialism across both rationalist and reflectivist approaches. It shows that, despite their differences, these approaches remain grounded in a shared commitment to separability, thereby limiting the possibility of post-binary analysis. In response, the chapter develops Trialectics as a nondualist methodological model that introduces a third dimension of reality—“single hidden oneness”—which underlies and connects the apparent duality of subjects and objects. Rather than resolving oppositions through synthesis, Trialectics reorients enquiry towards a three-dimensional understanding of relationality in which contradiction and complementarity coexist within a deeper unity. This framework is operationalised through the trialectical diagnostic technique (TDT), which examines shifting relations, engages with epistemic gaps without reifying them, and foregrounds the intermediary zone through which post-binary understanding emerges. Applied to global environmental politics, the chapter demonstrates how Trialectics enables a reconfiguration of entrenched dualisms—such as global/local, human/nature, and West/non-West—by advancing a relational and integrative approach to global responsibility.