§ 5. Natural Signs as Instruments of Conceptual Thinking. — Expression by natural signs fulfils the essential function of language as a means of conceptual analysis and synthesis; by it the content of concrete experience is resolved into relatively elementary constituents which are freely recombined in new ideal structures. That the signs of gesturelanguage bring with them an apprehension of the general or universal aspects as distinct from the particular and specific details of perceptual experience is plain from their very nature. An imitative gesture can only suggest general characters or features common to a class of objects or actions. The thought it expresses or evokes is only a fragment of a thought and demands completion. It is indeterminate and requires further definition from a context expressed or understood. The context itself consists of other imitative gestures, each expressing a relatively indeterminate universal. Each of these relatively indeterminate universals particularises and defines the others, and is by them particularised and defined. Just as we can illustrate this process by taking at random any intelligible combination of conventional words, so we can illustrate it by taking at random any intelligible combination of imitative gestures. The analogy holds good in another respect also. The natural sign, like the conventional word, becomes modified in meaning in varying contexts and under varying circumstances.

We may illustrate both points simultaneously. An acquaintance of Colonel Mallery's once asked the same favour of two chiefs successively. Each in replying used the common sign for repletion after eating, — "viz. the index and thumb turned towards the body, passed up from the abdomen to the throat; but in the one case being made with a gentle motion and pleasant look, it meant 'I am satisfied,' and granted the request; in the other, made violently, with the accompaniment of a truculent frown, it read, 'I have had enough of that.' " Here the sign used for bodily repletion derives a metaphorical meaning from the context in both cases, and a different meaning in each.