This article explores the dialectical relationship between liberating trust in reality and religious faith in God, interpreted from a Christian-Muslim perspective. An underlying conviction is that liberation constitutes a necessary mutual correlate of a "true" religiosity, i.e., liberation is to be conceived as both prerequisite for and realization of a genuine religiosity, and vice versa. As opposed to a "true" religiosity, born from liberating trust and finding its fulfilment in prophetic action aimed at liberation of human realities, religious belief and practice that stem from fundamental mistrust are likely to deteriorate into either religious fundamentalism or indifferentism. The article focuses on fundamental trust in reality as capable of evoking the liberating and uniting force of religious theory and praxis. It aims to render explicit the religious and ecumenical potential (hitherto not fully realized) of the theological-ethical considerations of Hans Küng, in particular within a Christian-Muslim framework. The first part of the article, more conceptual in character, examines Küng"s views on fundamental (mis)trust and its religious implications. The second part seeks to identify theological insights that shed light on the specifically Christian and specifically Muslim interpretations of liberating trust. My hope is that this study may contribute to a truly global ecumenism whose objective is to render religion an instrument of liberation, not oppression.