In this essay, I critically examine Habermas’ approach to fundamentalism, a question that explicitly and implicitly alike bears influence on the formation of his postsecular thesis. The overview of his theory is followed by a combined analysis, depending on Torkel Brekke’s sociological study on fundamentalism, on the one hand, and a joint study by Adam Seligman and others in the field of anthropology and social theory. In this regard, questions of sincerity and authenticity are in the focus of my examination, (...) underlying that philosophical relevance of the question. On the basis of this combined analysis I argue that fundamentalism can be best analysed as an essential though specific element of modernity. I state that despite its critical attitude towards many developments of modernity, fundamentalism is not only reactively but, in its attitudinal core, a proactively modern phenomenon, and needs be interpreted accordingly as part of the evolving postsecular scenario. (shrink)