For van der Leeuw, understanding is the subjective aspect of phenomena,
which is inherently intertwined with the objectivity of that which is manifest. Van der Leeuw articulates the relation of understanding to understood phenomena according to the schema outlined in Dilthey’s definition of the human sciences (Geisteswissenschaften) as sciences that are “based on the relations between experience, expression and understanding” (“Verhältnis von Erlebnis, Ausdruck, und Verstehen”). Van der Leeuw correlates subjective experience, expression, and understanding with three objective levels of appearing—relative concealment (Verborgenheit), relative transparency (Durchsichtigkeit), and gradually becoming manifest or revealed (Offenbarwerden), wherein the understanding of what is becoming revealed is the primordial level of appearing from which the experienced concealment and expressed transparency of appearing are derived.
Because van der Leeuw, like Kristensen, appropriates Otto’s concept of das Heilige in defining the essential category of religion, the transcendence becoming revealed in all human understanding can be further described as sacred — an overpowering “wholly other,” which becomes revealed in astonishing moments of dreadful awe (Scheu) and wonderful fascination. Van der Leeuw argues that this concept of religious dread is also present in Kierkegaard’s work onAngst and in Heidegger’s statement that “what arouses dread is ‘being in the world’ itself”. Moreover, van der Leeuw recognizes that, although dreadful, Being-in-the-world is fundamentally characterized as care (Sorge), the existential structure whereby Dasein is concerned with meaningful relationships in the world alongside other beings.
Because all experiences disclose concealed (wholly other) transcendence to the understanding, all experiences of Being-in-the-world are ultimately religious experiences of the sacred, whether explicitly recognized as such or not. Human being as such is homo religiosus, the opposite of homo negligens.
It is the task of the phenomenology of religion to interpret the various ways in which the sacred appears to human beings in the world, the ways in which humans understand and care for that which is revealed to them, for that which is ultimately wholly other mystery. Among other great phenomenologists who worked and influenced phenomenology of religion are Kristensen, Henry Corbin, Mahmoud Khatami, Ninian Smart, de la saussaye, Mircea Eliade.