 One consequence of the conventional nature of language, according to which the relation between a sign and a significate is imposed on the sign by a voluntary act on the part of the impositor, is that the change in what is signified by the sign does not require a change in the sign (NLPery I.1; Lewry 1981). On the other contrary, in the case of natural signs, such as paleness from fear or redness from shame, the change in the thing signified implies a change of its  sign.[27]