Asanga (5th century AD, b. Puruṣapura, India) was an influential Buddhist philosopher who established the Yogacara school of idealism that held that the external world exists only as mental images that have no real permanence. His brother was Vasubandhu who, before he encountered the Mahayana, authored the Abhidharmakosa.
“As so often happens, it is very hard to really grasp or understand what Asanga was like as a person and what events really took place in his life because he lived roughly in the fifth century and historical facts seems to be somewhat secondary in this case. So many myths and legends revolve around a person who lived in such a remote age. Once we dispense with that we get to the Abhidharmasamuccaya. Asanga composed a lot of texts and among them the Abhidharmasamuccaya has a very prominent position. It is one of his most essential works and one of the most psychologically oriented works, which provides a framework as well as a general pattern, for how a practitioner should follow the path, develop him or herself, and finally attain buddhahood.” -Traleg Kyabgon Rinpoche