Image & its relationship with theory in Waltz's thought

Up to 1960s Behaviorism dominated epistemologically the academic spheres of social sciences including International Relations. It held, given the discoverable a prior order in reality, scientist was able to find out "outside" objectively, by withdrawing the subjectivity.Waltz was the first who applied systemic approach to International Relations. Moreover, tended to the recent attitudes of Philosophy of science, the separate of subject and object is idiotic for him. So, in addition to alternate "level of analysis" with "image", to show coinfluence of subject and object to each other’s, he introduced systemicapproach to "three images" as the best to explain world politics. In this article, first, these issues would be presented: what is "level-ofanalysis"(image), its place and its application in Waltz's theory? Then, it is going to be explained why waltz was inclined to replace "level-ofanalysis" with "image"?