This paper discusses the relations between secularism, religion and nationalism in Israel and offers a thesis about the failure of secularism there. The papers adopts Michael Mann's view of "religion" as a private case of ideological network of power and suggests a typology of four possible heuristic modules of political legitimacy, which are composed of different blends of nationalism and religionism (the suffix "ism" is added to underline Mann's view of religion as an ideology). These modules are constructed by the crosscutting of two axes: the axis of nationalism, which taps "weak" to "strong" nationalism, and the axis of religionism, which taps "weak" to "strong" religion (wherein the ultimate case of "weak religion" means secularism). The four modules are the following: strong nationalism/weak religionism: this is the case of a dominant and energetic secular nationalism. Strong nationalism/strong religionism: this is the case of a fusion between strong nationalism and strong religionism, which creates a kind of indissoluble mesh of "religious nationalism". Weak nationalism/weak religionism: this module represents a polity which is not founded upon strong pre-political "primordial" or ascriptive, national or religious, communal identity, but is rather constitutionally or "contractually" oriented. Weak nationalism/strong religionism: historically, this combination represents pre-modern and thus pre-national cultures, in which religion was pervasive as a communal identity. Presently, this combination can represent a type of communal "post-nationalism" or a transnational fundamentalism. The paper explains how Israeli political culture had moved from the type of strong nationalism/weak religionism to the type of strong nationalism/ strong religionism, which is inimical to secularism.Keywords Israel . Nationalism . Religion . Secularism This paper discusses the relations between secularism, religion, and nationalism in Israel and offers a thesis about the failure of secularism there; a failure "in the last instance," so to speak, because in the "first instance," say 60 years ago, observers tended to assess that Int J Polit Cult Soc (2008) 21:57-73