In this article, the ?jadal? (dialectic) which its foundation dates back to the Grecian philosophy what had meant before Ash?ari and how to be understood in his system has been comparatively explained. In the meantime, the concepts of nazar and muarada in Ash?ari?s dialectical system have been mentioned and also the common points and differences of these concepts have been discussed. Finally, the contribution of Ash?ari?s to the science of jadal has been considered.