Recent science reform documents have called for incorporating authentic scientific discourse into science classes as engaging in discourse has shown to result in numerous benefits. Whether these benefits are observed in students depends upon the quality of the discourse in which they engage. However, characterizing the quality of student-student discourse can be an ambiguous task. In this work, we introduce decentering as one feature of effective student-student interactions that can be used to evaluate the quality of discourse. Decentering refers to the process of differentiating between one's own perspective and another's. Arguments from two process-oriented guided inquiry learning physical chemistry classes are presented to illustrate this concept. Decentering manifests itself in these arguments through careful consideration of alternative arguments. Practitioners and researchers can use the results of this study to facilitate and analyze student-student discourse.