It is also important to distinguish the dual/common coding debate from the better known (at least to philosophers), and ongoing, analog versus propositional debate about imagery, which arose a few years later, in the early 1970s (and will be covered in section 4.4). Although these two controversies did become very entangled, the main points at issue are quite different, and an explicit awareness of this may help us avoid some of the confusions that arose from the entanglement. The analog/propositional debate concerns the nature of imagery itself (to put it very crudely, the analog side thinks mental images are inner pictures, and the propositional side think they are inner descriptions), whereas the dual/common coding debate concerns the functional role played by imagery in the cognitive processes of memory and thought. It may be true that that, amongst cognitive scientists, Dual Coding Theory is most often associated with an analog conception of imagery, and common coding is associated with the propositional conception. However, given that Paivio conceives of his verbal code to be embodied as natural language, inner speech, there seems to be no reason to think that it is incoherent to combine a propositional view of imagery with a form of Dual Coding Theory, as Baylor (1972) and Kieras (1978) have proposed. There also appear to be no prima facie reasons to think that the enactive theory of imagery (see §4.5.1 of the main entry) might be inconsistent with Dual Coding. Furthermore, although perhaps no contemporary theorists combine an analog theory of imagery with a common coding theory of memory, it is arguable that this view was implicit in many of the cognitive theories of former times. For instance, Empiricist philosophers such as Berkeley and Hume (and, very arguably, Aristotle) thought of images as being picture-like (analog), and held that all memories (indeed, all mental contents, all ideas) are images of some sort (common code)