In light of Martin Heidegger's contextualized influence upon them, John Macquarrie, Rudolf Bultmann, Paul Tillich, and Karl Rahner engage in theologies that, in their respective tasks and scopes, venture into existential theology, following Heideggerian pathmarks toward the primordiality of being on the way to unconcealment, or "aletheia." By way of each pathmark, each existential theologian assumes a specific theological stance that utilizes a decidedly existential lens. While the former certainly grounds them fundamentally in a kind of theology, the latter, by way of Heideggerian influences, allows them to venture beyond any traditional theological framework with the use of philosophical suppositions and propositions. In an effort at explaining the relationship between humanity's "being" and God's "Being," each existential theologian examines what it means to be human, not strictly in terms of theology, but as it is tied inextricably to an understanding of the philosophy of existence: the concept of what being is.