 Thus, language of action and analysis of ideas mutually enrich each other, according to a hierarchy of needs (at first, communication will be about food and immediate dangers). The decomposing of signs matching the analysis of ideas leads to the creation of new signs, following a rule of analogy with the signs already known and this process allows the consideration of further ideas. Conversely, no consideration of more refined ideas would be possible without the corresponding signs. An example that Condillac favors is that of the system of numeration based on the ten fingers, which allows for the progress of arithmetic: a single finger is first used to designate the unit but can subsequently be used for designating 10, 100, and so on (Language of Calculi I.1).