Tier 2: Material Potentialities

Tier 2: Material Potentialities is the second band of the Tower's seven-tier classification scheme, reserved for subjects that possess the capacity to become material but have not yet done so. It is distinguished from Tier Alpha, which holds subjects wholly exhausted by description, and from Tier III: Demonstrative Models, which holds subjects that have already demonstrated a material form at least once. A Tier 2 holding is neither: it is registered, measured, and cross-referenced, but its materialisation remains an open question carried forward indefinitely. Floor audits conducted every eleven years have consistently placed Tier 2 holdings at between four and six per cent of the catalogue, though the figure is disputed by the Census Bureau, which counts differently.

Definition and scope

The tier was established under Concordance 41-B, which defines a Tier 2 subject as "any catalogue entry for which a material instantiation is coherently foreseeable but has not been observed." The definition is deliberately broad, and in practice Tier 2 has absorbed holdings ranging from engineered alloys whose fabrication lapses have gone unrecorded, to rooms described in sufficient detail that their construction is judged feasible, to objects that appear only in the marginalia of other entries but are nonetheless attested as buildable.

Classification is performed by the Office of Tier Assignment on the basis of a Material Feasibility Return, a three-page form in which the auditor states whether the subject could be made, and if so, on what floor. Feasibility is graded from A to E. Grade A subjects require no unusual apparatus; Grade E subjects require an apparatus that does not itself exist, which is permitted provided that the apparatus is separately registered at Tier 2 or above. Circular chains of Grade E feasibility are discouraged but not forbidden, and at least nine such chains are currently open.

Relationship to the Great Ledger of Potentialities

Tier 2 is administratively downstream of the Great Ledger of Potentialities, which records subjects at the moment of their pre-emptive inscription. The pre-emptive inscription of potentialities creates a designation string; Tier 2 assignment creates a shelf. The distinction matters because inscription is subordinate only to the authority of the Eleventh Librarian, whereas tier assignment may be appealed to any Tier II reviewing clerk. Approximately 71 per cent of Tier 2 holdings carry a Ledger designation string of the second form (P- prefixed, followed by four numerals and a spiral mark); the remainder, mostly older holdings, are filed under the obsolete first form and have not been migrated.

Holdings that lose their potentiality — because the subject is found to be impossible, or because it is found to have been material all along — are transferred out. The former route leads to the Archives of Extinct Possibilities; the latter leads upward to Tier III. Transfers between these destinations and Tier 2 require a Form 1747-Ω countersigned by two clerks of the Department of Material Causality, a requirement introduced after the Halloran Recount of 1188 found fourteen holdings filing in both directions simultaneously.

Handling and storage

Tier 2 holdings cannot be shelved in the conventional sense, since they occupy no verified extent. They are instead held in posting frames: open-fronted cabinets, 40 centimetres deep and 90 centimetres wide, fitted with a brass designation plate and a small drawer for the feasibility return. The frames hold no object. Clerks are required to confirm once per shift that each frame remains empty, and to initial the posting log accordingly. Persistent non-emptiness in a frame is treated as a materialisation event and triggers the Gamma Report procedure by which Tier IV retirement is normally requested.

Posting frames are arranged in bays of twelve. Bays are assigned to Tier 2 as a whole rather than to individual holdings, a practice begun during the Second Bay Consolidation and never revised. The consequence is that a Tier 2 holding's physical situation on the floor bears no relation to its Ledger designation, and retrieval of a feasibility return may take a clerk several hours. A proposal to reorder the frames alphabetically has been tabled at each of the last six sessions of the Standing Committee on Shelf Order and has not yet been read to a vote.

Methodological dispute

The status of Tier 2 holdings that are never materialised is a matter of continuing disagreement. The Doctrine of Coexistent Potentialities, as applied by Division VI: Unallocated Phenomena, holds that an unmaterialised subject retains full potentiality indefinitely and should remain at Tier 2 without review. Against this, Concordance 88-C provides that a subject unmaterialised for ninety years shall be presumed extinct and removed to the Archives of Extinct Possibilities, with a right of reinstatement on evidence.

The Census of Potentialities drew its methodology from the Doctrine and accordingly counted long-dormant holdings as live; the Census results were later reabsorbed by the Great Ledger of Potentialities, which did not alter the underlying holdings. Critics of the Lapse provision observe that it has never been applied to any holding, since no clerk has been found willing to sign the extinction schedule; defenders reply that the provision's value is deterrent rather than operative. The Sensitive Material Review has declined to resolve the question, noting in its MAP-6 that the discrepancy falls outside its remit.

Selected holdings

The eleventh tread of P-2417-S29 has been the subject of an unresolved note in the posting log since 1204, in which a clerk observed that the frame appeared "a tread short." No materialisation has been recorded, and the note has been carried forward without amendment.