Although the innovative and systematic theory of substantial motion has been supported by its originator through numerous arguments, it also draws upon various evidences and corroborations provided by its founder. Among the most significant—and yet most peculiar—of these corroborations are the statements of Avicenna and some of his Peripatetic followers regarding certain types of accidental motion: namely, gradual intensification in quality (becoming black) and augmentative motion in quantity (increasing in magnitude). This article, employing an analytical-descriptive method, aims to provide a novel analysis of Mullā Ṣadrā’s philosophical process in constructing the edifice of substantial motion upon certain claims and implications held by its detractors. The article analyzes this process through several stages, concluding that, from Mullā Ṣadrā's perspective, the very justifying principle of intensificatory qualitative and augmentative quantitative motion—which hinges on the realization of fluid being—serves as a corroboration for the justifying principle of substantial motion. This is achieved not by way of logical analogy, but rather by removing the obstacles that Avicenna perceived in the path of substantial motion. Ṣadrā’s intensificatory substantial motion requires nothing beyond the fluid being —which is identical to both the motion and the moved—to maintain its individual unity.