s not to answer the metaphysical problem but rather to ignore it. If colours are in fact extended, as the Treatise continued to insist, yet the mind ultimately only knows its own sensations, however variously they might be transformed by cognitive processing, then we can only come to be in a position to attribute colours to external objects if we first experience those colours, which suggests that they must modify our being.
Though Condillac's official reply to the charge of materialism, as expressed in the letter to Lignac, is something of a disappointment, scholars have occasionally read the Treatise as taking some steps towards a more radical way of dealing with the problem. Recall that in that work Condillac advanced the view that even though colours are in fact extended and bounded, it is not intuitively evident that they are. We need to learn to see their shapes. Interestingly, what teaches us to see these shapes are tactile sensations of solidity and observations of the appearance and disappearance of colours consequent upon moving our hands before our eyes. Since neither sensations of solidity nor the tactile sensations that accompany hand motions not patently extensive in character, and colours themselves might as well not be so far as the early learner is concerned, some scholars have suggested that the Condillac of the Treatise meant to claim that our perceptions of space are constructed from raw data that, as they are at first experienced by the mind, are in no way spatial. Insofar as the Treatise does move towards this more radical view, it can be seen as a precursor of such 19th century Berkeleyan theories of vision as those of Steinbuch, Mill, Helmholtz, and Wundt. However, those later theories invoked notions of local signs (sensations specific to which nerve is being stimulated) and made explicit appeals to kinaesthetic sensations that are simply absent from Condillac's work. Lacking those notions, Condillac claimed that an awareness of space cannot be generated from aspatial sensations, and he represented his statue, not as constructing space, but as discovering the spatial features that were already present in its sensations from the first. Viewing him as a precursor of 19th century Berkeleyanism risks overlooking this fact and, as a consequence, misrepresenting his thought.
In both the Essay and the Treatise Condillac set out to show that all of our cognitive and conative faculties are generated from sensation and can be derived from that operation alone. To this end he identified perception, consciousness, and attention as all being different aspects of the one operation of sensation. Perception is the impression sensation makes upon the mind, consciousness is this impression considered as something experienced by the mind, and attention is simply a more vivid perception. But when Condillac came to account for memory and reminiscence, this project stalled. It is not implausible to maintain that a sensation might continue to be experienced after the object that occasioned it has ceased to act on the sense organ. But such an “echo” of a past sensation is itself a present phenomenon. It might be fainter than other sensations that are now occurring, but being experienced to be faint is not the same thing as being thought to have originated in the past. Rather than explain how sensation can give rise to an awareness of pastness Condillac simply helped himself to the notion. In the Essay, he defined “reminiscence” as the awareness that a perception has been had “before” without anywhere explaining how the idea that one thing can be “before” another could arise simply from sensation (Essay I.ii.1. §15). In the Treatise he distinguished the memory of a sensation from a current sensation by calling the former “weakly sensing what one was (sentir foiblement ce qu'elle a été)” and the latter “vividly sensing what one is (sentir vivement ce qu'elle est).” But then he immediately went on to say that recalled sensations can sometimes be more vivid than current ones (Treatise I.ii.8–9). So what necessarily distingu