Mnemonic Constancy

Mnemonic Constancy is the property by which a catalogued thing continues to be remembered in exactly the form in which it was first indexed, irrespective of how often it is recalled, cited, or copied. It is distinct from mere persistence, which the Tower treats as a question of storage, and from fidelity, which is a question of transcription. Mnemonic Constancy concerns the memory itself: whether a holding, having entered the archive, remains the same holding in every subsequent act of consultation. The principle is maintained under The Constancy Principle and verified, where verification is possible, by instruments of the Caliper class.

The doctrine is not native to the Tower. It was received, in the form now standard, from the School of Absolute Constancy, and the School's influence is visible in almost every later instrument of the archive, including the Theorem of Referential Constancy that governs calibration.

Definition and scope

Mnemonic Constancy is defined in the Fourth Concordance, Annex 2, as "the invariance of a holding under repeated remembrance, in respect of its designation, its extent, and its relations." The definition is deliberately narrow. It says nothing about whether the holding is true, useful, or even internally coherent; a thoroughly false record may enjoy perfect Mnemonic Constancy, and several do. What the definition protects is the record's identity across time — that the clerk who consults a floor on one day and the clerk who consults it a decade later are consulting the same floor.

The property is assessed along three axes. Designation concerns the name and number of a holding and is the axis most frequently found wanting. Extent concerns the holding's boundaries: where an article ends, what it includes, and what has been silently annexed to it. Relation concerns the holding's cross-references, and is the axis on which the archive is most vulnerable, since every new article alters the relations of the articles that link to it.

The measurement of constancy

No instrument measures Mnemonic Constancy directly. The Caliper of Dimensional Constancy measures dimensional drift, which is a proxy, and the Caliper Masters have long maintained that the proxy is adequate because a holding that does not drift dimensionally cannot have drifted mnemonic ally. This reasoning has been challenged, notably by the Ontological Formalists, who observe that a record may hold its exact dimensions while its meaning has been entirely replaced — a fault they term "constancy without continuance."

The dispute is not purely academic. In the winter of the year the archive records as 14-Kappa, a consignment of Mnemonic Tape destined for the Hall of Provisional Whispers was measured on receipt and found to be within tolerance on every axis the Caliper records. On threading, however, the tape proved to carry the text of a floor that had never been indexed. The consignment was returned. The receiving clerk, Clerk Amaranth Vey, noted in the margin of the receipt that "the tape was constant; it was simply constant about the wrong thing," and the phrase entered the standing vocabulary of the Directorate of Dimensional Fidelity.

The Resin question

For most of the archive's history Mnemonic Constancy was held to inhere in the holding itself. This position, the Inherence Doctrine, was displaced in stages by the Carrier Doctrine, which holds that constancy inheres in the medium and is lent to the text it carries. The decisive evidence was the Everburning Candle, whose clarified Silentium Resin was found to preserve not only illumination but the mnemonic state of anything kept beneath it. A lamp that reminds is a stronger claim than a record that remembers.

"Where the medium is constant, the text is constant, and it is of no consequence what the text says."

— Seventh Concordance, Annex 11, "On the Priority of the Carrier"

The Carrier Doctrine has never been fully reconciled with the Third Concordance, which retains the older language of inherence and has not been amended. The contradiction is acknowledged in practice: the Concordance Office instructs that the Third be cited when the medium is in dispute and the Seventh when it is not, a rule that resolves nothing and has settled every case brought under it.

Constancy in the Mnemonic Labyrinth

Nowhere is Mnemonic Constancy tested so severely as on Floor 14,302, the Mnemonic Labyrinth, where the Department of Ephemeral Taxonomies is headquartered. The Department's holdings are by definition transient — things catalogued in the act of disappearing — and the conflict between transience and constancy is managed by a standing protocol, Standard Operating Protocol 12-Alpha, which provides that every ephemeral holding be given a fixed designation before its catalogue entry is begun. The protocol has been amended four times, always in the direction of earlier designation.

Even so, the Labyrinth returns periodic failures. The most-cited is the case of the vanishing stairwell, indexed on a Tuesday and unfindable by Thursday though its designation remained in force and its entry unaltered. The Department's report attributes the loss to "constancy of record without continuance of object," a distinction that the School of Absolute Constancy has refused to recognize and that the Archive nevertheless now prints in its own heading type.

Recorded failures

Three failure modes are recognized in the standing literature. Drift is the slow divergence of a holding from its indexed extent, measurable and correctable. Substitution is the replacement of a holding by another of identical dimensions, detectable only by consultation. Collapse is the abrupt loss of a holding's relations while its designation and extent survive, producing an article that cites nothing and is cited by no one — the archive's equivalent of a room with no doors.

Collapse is the rarest and the least tractable. The Vault of Absolute Constancy, which houses the Standard Temporal Unit on Transfer Floor 19-Kappa, is maintained specifically as a control against it: the Unit is consulted daily, its constancy attested, and the attestation filed. No instance of collapse has occurred within the Vault. The arrangement is felt to be sufficient, and a request to extend the daily reading to other floors was refused in the year 16-Sigma on grounds of staffing.

Practical guidance for clerks who suspect collapse is brief. A holding whose links have failed is to be re-linked once by hand, and if it fails a second time, left alone. The instruction is printed on the reverse of the standard Mnemonic Tape spool label.