In the eyes of many, "spirituality," particularly in its non-religious form, is nothing but a secularized, individualized, or even commodified version of traditional religion. Against these pejorative and dismissive conceptions, this book seeks to take seriously the notion of "spiritual but not religious" as a philosophical concept which can illuminate different aspects of human experience or even uncover a primordial sense of "spirituality" that lies at the heart of human existence. Spiritual Life and Secular Thought puts forward a new philosophical definition of spirituality applicable to both religious and non-religious outlooks alike. It proposes that spirituality may be construed as the pursuit of the unity of life and thought. Drawing on phenomenological insights from Martin Heidegger, Hannah Arendt, Gilles Deleuze, and Giorgio Agamben, Spiritual Life and Secular Thought argues that "non-religious spirituality" is not just an outworking of post-religious individualism or spiritual consumerism, but an expression of fundamental dimensions of human existence and the experience of living and thinking in the world. This proposed existential phenomenological notion of spirituality as the unity of life and thought not only paves the way for renewed assessments of the relation between philosophy, spirituality, and religion in secular society, but also sheds new light on how one might live and think spiritually in the contemporary world.