Refining the core premise of the semantic argument

The core premise of my semantic argument holds that two concepts that share the same reference set also share the same meaning. The first consideration I offer in support of this premise is that two concepts that share the same reference set cannot be distinguished by examining the references of their component concepts. In both cases, we encounter precisely the same set of objects in the world. So, both concepts relate to the objects in the world in the same manner, when considered in terms of their constituent components. Given that meaning and reference must, in any case, be related, this provides a reasonable indication that the meanings of both concepts are the same. This consideration implicitly assumes, of course, that both concepts do in fact relate to the world. The scope of the semantic argument is thus reasonably confined to concepts that actually relate to the world and hence refer to at least one object in the world. Therefore, the core premise is reasonably limited to concepts having existential import. Concepts whose extension is empty are thus excluded from the scope of the semantic argument. This scope limitation of the core premise rules out certain alleged counterexamples. Consider, for instance, the concepts 'humans with orange blood' and 'humans with yellow blood'. Assuming that neither orange nor yellow blood exists in the actual world, the reference sets of both concepts - namely, on the one hand the set of all humans and all occurrences of orange blood in the world and on the other hand the set of all humans and all occurrences of yellow blood in the world - are the same, while both concepts clearly differ in meaning. Nonetheless, alleged counterexamples such as these do not undermine my semantic argument, as both concepts have an empty reference and thus fall outside the scope of the semantic argument's core premise.