The global justice debate has increasingly moved toward the analysis of concrete issues in global politics, such as trade, migration, or climate change. This raises a methodological question: should the demands of justice in these domains be theorized independently or in conjunction with one another? Integrationists have championed the latter approach, arguing that it is better suited to guide our practical judgments. In contrast, internalists maintain that each domain is governed by its own set of principles. This paper defends the plausibility of the internalist approach against integrationist challenges. By examining different interpretations of internalism, it first seeks to provide a clearer overview of the methodological dispute. It then analyzes various arguments for integrationism, showing that their implications are more limited than their proponents believe. Finally, it focuses on the question of practical guidance, highlighting the value of idealized domain-specific theorizing in guiding transitions toward just arrangements.