Abstract: Up to now， most linguistic scholars tend to take iconicity and arbitrariness as a pair of concepts which are contradictory to each other. However， an agreement on the understanding of iconicity has not been reached. It is theoretically constructive to explore the nature of asymmetric negation by making a binary segmentation to the traditional iconicity which may be cut into mapping iconicity and motivational iconicity. Correspondingly， arbitrariness means a non-necessary mapping relationship. That mapping iconicity constitutes the contradictory concept to arbitrariness， once approved， will directly negate the arbitrariness， but the language facts don't sustain this decisive relationship between the signifier and the signified. Meanwhile， motivation is not a subordinate category of iconicity， but a subordinate category of arbitrariness. Despite the language evidence proving that motivation could be found between the signifier and the signified， the motivational iconicity's existence is premised on the existence of arbitrariness. And it is a choice under the principle of arbitrariness. Therefore， instead of disproving arbitrariness， motivational evidence proves the rationality of arbitrariness.

Key words: iconicity, arbitrariness, motivation, asymmetric negation