Conceptual Overload

Conceptual Overload is the condition in which the conceptual mass borne by a surface, structure, or corridor exceeds the load for which it has been rated in Standard Conceptual Units (SCU). It is distinguished from adjacent phenomena — from Conceptual Contamination, which concerns unwanted mixture rather than excess, and from Conceptual Motility, which concerns movement rather than weight — by the strict criterion that an overload is measured, while the others are merely observed. The condition is the most frequent cause of Conceptual Integrity failure recorded in the Tower, and the least frequently prevented.

The first systematic treatment appears in Third Concordance, Annex 9, which fixes the working figure of 40 SCU per square cubit for inhabited flooring and notes in its margin that "the figure has been found sufficient in every case in which it has been tested and in no case in which it has not" (Librarian Ordwin Hall, Marginalia on Annex 9, 118-AP).

Measurement and Rating

Conceptual load is assessed by the Specificity Analysis method, in which a sample of a surface is asked what it is until it stops answering in general terms. The depth at which the answers become specific is taken as a proxy for mass and converted to Standard Conceptual Units by a table maintained by the Bureau of Conceptual Reconciliation. The table has been reissued eleven times; the eleventh reissue reduced the conversion for questions asked in winter, on the grounds that cold surfaces answer more slowly and should not be penalised for it.

Rating is the responsibility of the Office of Load and Tolerances, which assigns each floor a ceiling value and stamps it into the door jamb of the principal stair. A floor rated at 3,000 SCU that receives 3,100 SCU in a season does not fail immediately. It sags, records what it was carrying in a somewhat lower voice, and must then be reported.

The Splenic Swamp Collapse

The canonical instance remains the Splenic Swamp Coherence Collapse of 211-AP on Floor 45, where conceptual pilings were found to have been carrying not only the material above them but also the accumulated cataloguing of that material, a quantity no survey had thought to include. The post-collapse inquiry sat for nine sessions and produced the finding that pilings should be rated against what is actually resting on them rather than what is meant to be resting on them, a recommendation the Office of Load and Tolerances declined to adopt on the grounds that it could not be implemented without moving the material first.

Where overload is anticipated, the customary remedy is Conceptual Zoning, which redistributes load by adjacency and is scheduled precisely to prevent Conceptual Dilution. The remedy is not always well received by the floors concerned. In the winter of 244-AP, a zoning schedule intended to relieve pressure on the ninth landing of Stairwell Beta moved a portion of the landing's load onto Floor 909, already under strain from an accumulation of uncatalogued absences. The resulting objection, filed by Clerk Ambrine Vosk and running to sixty-one pages, is preserved chiefly for its closing line: "The absence of a thing is not lighter than the thing" (Vosk, Objection to Schedule 12, 244-AP). The schedule was upheld on appeal; Vosk was reassigned to Floor 3,312 and has not been heard from in the record since.

Overload in Substrates

Conceptual Soils are the most overload-prone material on the Tower's inventory, because they are defined as "sedimentary accumulations possessing coherent, albeit granular, conceptual mass" and because the process that forms them — the weathering of Conceptual Laminates — continues whether or not anything is standing on the result. An unzoned bed of Soils will accept Conceptual Infusion past its rated capacity without complaint until the moment it will not, and the moment is generally discovered by whoever was standing on it.

The Conceptual Aquifer beneath the lower agricultural floors presents the same problem in solution. Large-Scale Conceptual Press operations above an aquifer must be suspended during any period in which the aquifer's own burden is being measured, since the two measurements interfere. This suspension was made mandatory by Seventeenth Concordance, Clause 44, and is the only clause in the Concordances to have been enacted on the testimony of a single witness — a drain-keeper on the sixth agricultural floor who reported that the water had begun to taste of the presses and was not believed, then was, then was believed at length.

Failure and Symptoms

Conceptual Integrity fails along the lines of least resistance, which in practice are the labels. Overloaded surfaces lose their names before their shape. A floor at 140 per cent of rating will continue to bear weight and continue to be walked on, but its designation will drift: signs will be found to read slightly wrongly in the morning, and correction of the signs does not prevent the drift. The Office of Load and Tolerances advises that drifting designations be left in place until the load is reduced, as painting over them adds, in the office's phrase, "a layer."

Where overload persists, it is conventional to record the affected surface in the Register of Straining Surfaces, a ledger kept in the ordinary way and consulted rarely.

"A floor is not required to announce its ceiling. It is required to hold. Notice is a courtesy the Tower has never guaranteed."

— Sixth Concordance, Annex 2, on the duties of load-bearing fabric

Doctrine and Dispute

The principal scholarly dispute turns on whether Overload is a property of the surface or of the catalogue. Ninth Concordance, Clause 12 holds that an object's conceptual mass is inherent and travels with it, so that loading a floor is simply accumulating. Fourteenth Concordance, Clause 3, written after the Splenic Swamp inquiry, holds that mass is conferred by description and that a floor is therefore loaded not by what it holds but by what has been written about what it holds. The two positions have never been reconciled, and the compilers of the Bureau of Conceptual Reconciliation have declined to reconcile them, observing in their annual note of 260-AP that "the Tower is not measurably worse for the disagreement, and is measurably better employed by it."

The practical consequence is that a floor may be in compliance with one Concordance and in breach of the other, a condition known as Equivocal Loading and resolved on the floor itself, by the simple expedient of finding out whether it holds. Visiting surveyors are reminded that the Office of Load and Tolerances requires two clear days' notice and that boots must be removed at the ninth landing of Stairwell Beta regardless of what is being carried.