Wrathall’s planks are not uncontroversial. In particular, his account of how second-plank unconcealment makes possible first-plank unconcealment is disputed, and I will offer an alternative to it in §9. Further, in §18 I will strike out Wrathall’s fourth plank, claiming that nothing further makes third-plank unconcealment possible in the way that a fourth plank would. Nonetheless, Wrathall’s planks are a useful starting point for my taxonomical project. They clearly distinguish different types or ‘levels’ of unconcealment—which I will turn into levels of unconcealing. The sharp distinction between the second and third planks is particularly important to maintain given the complicated relationship between discovering particular entities in their being (second plank) and disclosing the being of entities as such and as a whole (third plank). Further, the plank structure will force me to interrogate the relationships between each of the levels by asking how one makes the other possible, or how the other is grounded in the one (see §18). Finally, visualising Wrathall’s plank metaphor in a table sets me up with a certain set of rows and columns to which I can add further columns. I now turn to that—and so to setting up the basic structure of my taxonomy. Indeed, the first column to add brings us straight to a phenomenon of concealment.

As I noted, any unconcealing or unconcealment makes essential reference to a concealment that it presupposes and overcomes. Concealment ‘belongs essentially to unhiddenness [Unverborgenheit], like the valley belongs to the mountains’ (ET: 66/GA34: 90). Wrathall explains: ‘Unconcealment is meant to be understood like blindness or reticence. [. . .] With respect to each plank in the platform, then, concealment is the positive term, and needs to be understood before we can become clear about what unconcealment amounts

Heidegger on Being Self-Concealing by Katherine Withy