ished by convention. But Condillac had already explained how an artificial language can be instituted without innately understood signs (Essay II.i.1. §§1–4). Familiarity with the signification of natural signs, which are instinctively produced but not innately understood, will lead one to think of the sign upon witnessing the object that it signifies. For example, having learned to associate the cries that are made by those attacked by a wild animal with those circumstances, I will think of those cries upon seeing a wild animal approach and think of the effect that hearing them has previously had on myself and others. It is then a small, but momentous step to utter those cries in order, first, to signify the approach of a wild animal to others and induce them to flee, and then to signify this particular danger to oneself or others without bothering to imagine an approaching wild animal, as a way of abbreviating the process of thought. With this step, a move is made from being affected by accidental and natural signs we happen to chance upon in the course of experience to employing instituted signs to stand for experiences. The first stage in taking this step is the development of what Condillac called the “language of action,” a language composed of cries and gestures culled from natural language. A spoken language of arbitrary sounds and a written language are then gradually invented by users of the language of action (Essay II.i.1. §§5–8).
Since memory just is the imagination of signs, the development of instituted signs makes memory possible (natural and accidental signs are only ever sensed, not remembered). The institution of signs further allows us to set up names for groups of ideas that are too complicated to be distinctively yet collectively imagined, such as ideas of any number larger than six, of substances, of complex modes (notably moral and aesthetic qualities) and of genera and species of things (Essay I.iv). It is also supposed to give us control over our imagination and an ability to govern our attention (Essay I.ii.4. §46). This allows us to reflect on other aspects of our experience than those most immediately related to our needs. Reflection brings connections between objects to our attention that we would not otherwise notice and puts us in a position to refine our language by instituting names for what we have discovered. A more refined language facilitates yet more exact reflection, and language and our reflective capacities proceed to work in tandem to develop our cognitive abilities to their highest level (Essay I.ii.5).
In the Essay Condillac not only claimed that sensations are occasioned by the action of external objects on our sense organs, but also that they are images or representations of those objects. More precisely, he claimed that the objects that affect our sense organs must be extended and hence material things, though they may not have the precise shapes or sizes that our senses represent them as having, and though they do not have colours on their surfaces or bear qualities of smell and taste (Essay I.i.2. §§11–12). But if “we never leave ourselves and never perceive anything other than our own thoughts,” as Condillac claimed at the outset of the Essay (I.i.1. §1), then what could entitle us to maintain that our sensations bear this degree of resemblance to external objects or that there even is an external world containing objects that occasion our sensations?
In the Essay, Condillac contented himself with replying to this question by claiming that while we have a clear idea what it means to attribute extension to an object, we have no clear idea what it means to say that objects are coloured or scented, and that while there is evidence that proves that we do not always perceive the sizes or shapes of objects correctly, there is no evidence that proves that we are wrong to think that external objects have some form of extension (Essay I.i.2. §§11–13). Neither claim is compelling. Indeed, it is astounding how someone familiar with Descartes's dreaming argument could have made the 