For seven centuries scholars have speculated about the structural design of Dante’s Commedia but remain perplexed by the poem’s comprehensive ar-chitecture. This study undertakes a strictly empirical quantitative analysis of Dante’s magnum opus to address this lacuna. The outcome of this analysis enumerates the correspondence between the foundational rationale of the Commedia’s textual architecture and both physical and metaphysical concepts of Ptolemaic cosmology and Pythagorean principles of harmony and propor-tion as described by Boethius. The poem manifests a musically and mathemat-ically meticulous design conceptualized as musica universalis and expressed as musica instrumentalis that echoes Paschal and Marian plainchant. With an an-alytical synthesis of three components—Beatrice’s mathematical identity, the Trinitary ontology of the terza rima, and the quantitative properties of the Commedia’s canto lengths and their frequency of occurrence—this study de-crypts Dante’s comprehensive architectural design of a poem whose structural harmony continues to be felt by readers today.