This paper inquires into whether the three types of arguments usually formulated in the normative literature on the legitimacy of secession – i.e. communitarian, choice, and remedial arguments – are articulated (or not) by separatist parties in Catalonia and Scotland. It concludes that these actors do use such arguments, but they tend to merge them in different combinations making a pluralist case for independence rather than developing monist reasoning as most political philosophers do. Furthermore, it finds a fourth type of argument which is under-theorised in the relevant literature. This is an instrumental argument whereby independence is depicted not as an end in itself, but as a means to achieve better welfare and governance for the national population. It further proposes a fourfold theoretical scheme that links communitarian and choice arguments to a principled logic based on the belief in the existence of an absolute right to self-determination and remedial and instrumental arguments to a consequentialist logic that legitimates secession on the condition that it serves the achievement of specific ends.