This chapter introduces the beating heart of Tallis’ authorship: explicitness. Sections 1 and 2 are devoted to identifying some of the unique dimensions of his understanding of explicitness as compared to other more common conceptions. At the most basic level, explicitness for Tallis, is the transitioning of “what-is” to “that-it-is”, which, of course, doesn’t come immediately to mind when one thinks of explicitness—this rather exceptional notion I dub “T-explicitness” to mark its distinctive character. Section 2 deals with Tallis’ evolutionary story of T-explicitness’srise, highlighting the role of the human hand in birthing it. Section 3 introduces Tallis’ notion of the “Thatosphere”, a distinctively unprepossessing moniker that denotes the controversial extra-natural dimension of Tallis’ humanist naturalism, the “virtual outside” of nature that houses the intentional objects of T-explicitness. Section 4 concludes the discussion of T-explicitness and Sect. 5 offers a brief reflection on the interesting relationship between theology in the West and the need for T-explicitness.