Language ‘construction’ represents one of the facets of the speculative activities in the history of linguistics in the early modern period. It flourishes due to its rich grammars and glossaries of the European vernaculars and the idioms of distant countries. The formalization and use of vernaculars also for specialised communication is one of the reasons for questioning their validity as effective means for the acquisition and transmission of knowledge. In the 17th century the ‘utopistic’ desideratum of a universal, economic, and effective system of communication is attested by the numerous universal artificial language projects that were planned in order to improve international communication and, above all, man’s capacity to organise and produce new knowledge. In the present study the empiricist and rationalist views will be considered as the main distinguishing approaches to language creation. The continuity in the coexistence of two distinct stances characterize the theoretical perspectives that have extended also into the linguistic studies of the following centuries. In fact, the interpretations of the nature of the ‘units of thought’, how they are acquired and organised by the intellect, and then expressed, determine diverse standpoints in linguistic research which persist into contemporary theories, up until the 20th-century divergence between the formal versus the functional paradigm. With a focus on the speculation on artificial linguistic systems we will sketch a line of continuity from early modern into contemporary theories which involve the study of language (as an abstract system) and natural languages (as historical instances).