Principle of Material Coherence

The Principle of Material Coherence is the standing test by which the Bureau of Material Coherence determines whether a subject's internal relations hold under scrutiny. It is among the oldest instruments of assessment in continuous use in the Tower, and the only one whose wording has never been amended, a fact the Bureau cites with more frequency than the wording itself. By long convention the Principle is said to have been in force before any surviving document records it, and it is treated here in accordance with that convention.

Formulation and early status

The Principle is stated in the Third Recension of the Assessors' Manual, Clause 2.1, in the following terms:

"A subject is coherent if its internal relations hold when their sequence is removed from them. A subject is materially coherent if they hold with the sequence restored."

— Third Recension of the Assessors' Manual, Clause 2.1

The distinction drawn in the second sentence is the whole of the Principle's difficulty. The first test, coherence without sequence, may be applied by any Assessor of the Second Grade. The second test requires the Assessor to demonstrate that the relations would have held in some other sequence as well, or to state plainly that they would not, which few have been willing to do. The Principle of Material Coherence predates the Protocols for Coherence Assessment by at least a century, and the Protocols were drafted precisely because the second sentence had begun to receive inconsistent readings on floors too far apart to consult one another.

Relation to the Axiom

The Principle is properly understood as the operationalization of the broader Axiom of Material Coherence, which governs sequential causal chains in material manifestation. Where the Axiom is described by the Office of Material Coherence as a truth about how things come to be, the Principle is the instrument by which a clerk at a desk determines what to write in a register. That gap between truth and instrument has occupied the Tower for four hundred years and is not expected to close.

The Manual of Sequential Interpretation treats the Principle of Sequential Indeterminacy as the ninth of its principles and acknowledges in its preface that the two are "often discussed in tension with the Axiom of Material Coherence." Assessors working in the lower galleries habitually apply both, in whichever order the filing permits, and the resulting findings are filed under both headings.

Verification in practice

The Bureau of Material Coherence applies the Principle through a multi-step verification process: presentation, segregation, re-sequencing, and attestation. A provisional item is held apart from its claimed antecedents, described in a neutral register, and then restored to a sequence other than the one in which it was presented. If it survives restoration, it proceeds to a Material Coherence Attestation. If it does not, it is returned to the depositor with the offending relation marked in red ink and no explanation beyond the clause number.

Because attestation is a precondition of logistical support, the Principle determines in practice which items may be moved, and how far. The Bureau endorses calculations of Borrowed Coherence before a provisional item receives a Material Coherence Attestation, a requirement that the Bureau of Material Assessment has disputed in writing at least nine times. The Bureau of Material Assessment maintains that Borrowed Coherence is a fiction of the attestation process and cannot be its precondition; the Bureau of Material Coherence maintains that this objection is itself a demonstration of why Borrowed Coherence must be computed in advance. No joint ruling has been issued.

The Verrick dispute

The most vexed question in the Principle's history concerns its scope. The School of Literal Coherence holds that the Principle is an empirical instrument and applies to anything presented for assessment. The School of Strict Lineage holds, on the authority of the Concordance of Material Succession, Annex 7, that the Principle may be applied only to subjects whose lineage has been established, since a subject without lineage has no sequence to remove. The two schools have maintained their positions since 1087, when Assessor Halve Verrick offered a finding on a lacquer box that had been presented without provenance. Verrick subjected the box to the first test, found it coherent, and was censured for it. His reply, entered into the record, is still quoted:

"I did not establish the sequence. I removed it, and the relations held, and that is the whole of the first sentence."

— Halve Verrick, Censure Reply of 1087, f. 14r

The censure was never rescinded, but Verrick's formula is reproduced in the Assessors' Pocket Recension without attribution, which the School of Literal Coherence regards as an admission and the School of Strict Lineage regards as a copying error.

Later rulings

Successive amendments to the Protocols for Coherence Assessment have left Clause 2.1 untouched while regulating everything around it. The Ninth Librarian's Expedition attempted to reconcile perceptual anomalies with the Principle, recording 1,140 instances in which observers on the same floor described the same item in incompatible sequences. The Expedition's finding, that the Principle holds for items and not for observers, was received without comment and entered as Schedule 12.

In 1402 the Chamber of Dimensional Coherence submitted a request that the Principle be amended to cover subjects that hold in more than one dimension at once. The request was granted, the amendment drafted, and the amendment then withdrawn on the ground that the Concordance of Material Succession forbids amendments to unamended text. The Chamber's request remains on file. Assessors are asked to write "subject to the Guild question" in the margin of any such item, and the margin note has acquired a number of its own.

Maintenance

Working copies of the Principle are struck in black at the head of each assessment ledger. Copies are not to be taken above the Eleventh Gallery without the seal of a Librarian of the Third Grade. Clauses are read aloud at the opening of each session and are not to be paraphrased in the minutes.