This article problematizes the practice of relying on participant self-identification in research on religious, secular, and spiritual identity (RSSI) within the field of higher education, with particular attention to the implications related to participants who chose non-religious labels. While this practice is commonplace in the field, it is rooted in Western/Christian assumptions about foundational concepts such as self, agency, knowledge, and religion. The article describes alternative understandings of these concepts in order to point out the onto-epistemic biases present in existing higher education RSSI research. It goes on to share descriptive data about "non-religious" students from a qualitative study on RSSI themed intergroup dialogue courses. The way these students understood, and sometimes struggled with, the concepts of self, agency, knowledge, and religion illustrates why and how the exclusive reliance on RSSI self-identification can ultimately lead to the erasure of religious minorities and the perpetuation of a hegemonic Western/Christian-centric worldview.