Crossing the Indus Threshold A Falsifiable, Corpus-Wide Functional Decipherment of the Indus Script

This monograph presents the first complete, corpus-wide functional decipherment of the Indus Script, the last major undeciphered writing system of the Bronze Age. Using a constraint-driven computational framework, the work establishes a reproducible phonetic and grammatical scaffolding across the entire Harappan corpus without relying on assumed language identity, speculative semantics, or bilingual evidence. The study introduces two original analytical frameworks: LISSE (Linguistic Inspection of Sound Structure Environments), which assigns phonotactic envelopes (CV/CVC/V) to signs based on frequency class, positional behavior, and distributional constraints. LUCAS (Linguistic Understanding Construction Assembly System), which generates minimal, non-interpretive phonetic “shadows” compatible with attested South Asian phonotactic systems while remaining language-agnostic. All 417 Mahadevan signs, plus documented variants and structured buffer categories, are systematically mapped into a 500-sign functional inventory. The resulting model is validated against approximately 4,000 inscriptions, demonstrating consistent positional grammar, closed phonotactic systems, and formulaic administrative structures compatible with Bronze Age economic record-keeping. Key contributions include: A complete phonetic envelope mapping of the Indus Script corpus Identification of a stable administrative grammar operating with extreme textual compression (average inscription length ≈ 5 signs) Empirical documentation of terminal closure markers, numerical operators, role identifiers, commodity classifiers, and container validation sequences Corpus-wide entropy analysis demonstrating language-like structure and sequential predictability within known natural-language ranges Explicit falsifiability criteria allowing future discoveries to confirm, refine, or refute the model This work does not claim full semantic decipherment. Instead, it establishes what historical decipherments universally require before translation becomes possible: structural certainty. In this sense, Crossing the Indus Threshold situates the Indus Script at the same analytical stage once occupied by Linear B prior to Ventris and by Maya glyphs before phonetic confirmation. By grounding linguistic analysis in archaeological necessity, information theory, and full-corpus validation, this monograph moves Indus studies beyond pattern description into predictive, testable grammar. The result is not a speculative reading, but an operational model of how Harappan writing functioned. The threshold has been crossed. What remains is refinement, not uncertainty.