Vasubandhu’s formative years were steeped in the Sarvāstivāda Abhidharma tradition, and this early training left a deep imprint on the way he later articulated Yogācāra thought. Educated in a scholastic environment that treated dharmas as objectively existing and subjected them to meticulous classification, he developed a habit of rigorous analysis and a precise technical vocabulary. This background is clearly reflected in works such as the *Abhidharmakośa*, where a realist, external-world-affirming metaphysics is carefully laid out and examined. The very tools that were first used to defend Sarvāstivāda positions later became the instruments with which he would probe their limits and prepare the ground for a different vision of mind and reality.

Over time, critical engagement with alternative interpretations, especially those that questioned Sarvāstivāda realism, led him to reconsider the status of what appears as an external world. His dissatisfaction with the explanatory power of his inherited ontology, particularly regarding perception and subtle mental afflictions, opened him to Mahāyāna sources and to the emerging Yogācāra perspective. The influence of his elder brother Asaṅga was decisive here: through this familial connection he encountered a path that emphasized the bodhisattva ideal, compassion, and the transformative potential of consciousness. This encounter did not erase his Abhidharma training; rather, it redirected it toward a new center of gravity—consciousness-only (vijñaptimātra).

Thus, when Vasubandhu turned to Yogācāra, he did so not as a novice but as a seasoned Abhidharma master capable of systematically reinterpreting earlier doctrines. The analytic habits formed in Sarvāstivāda study allowed him to expose what he took to be logical tensions in realist accounts and to argue that what is taken as external reality is better understood as constructions or appearances within consciousness. In Yogācāra texts, this same precision is now harnessed to map the workings of mind, to explain how experience is structured, and to show how that structure can be purified for the sake of liberation. His background did not merely precede his Yogācāra views; it actively shaped their form, giving them both their critical edge and their remarkable clarity.