 One common misunderstanding of Carnap’s work on the theoretical language is an extension of the above-discussed misunderstandings of the Aufbau  (section 3  above). The Aufbau was traditionally perceived as an exercise in providing phenomenalist or empiricist foundations for scientific sentences. Therefore, it was assumed, the later work on both inductive logic and the theoretical language must be motivated by the aim of providing empiricist foundations for scientific sentences, to distinguish them from non-scientific, i.e., metaphysical sentences. This was certainly Popper’s view, for instance, and largely Quine’s, but they were not alone; it was widespread until the 1990s, when the new and more careful scholarship about logical empiricism began to take hold.