As a specialist in Yogācāra Buddhism, he has done extensive research in the area of Buddhist consciousness theory, recently publishing the book The Buddhist Unconscious: The ālaya-vijñāna in the Context of Indian Buddhist Thought. In connection with his interests in cognitive theory, Bill has also done interesting and extensive research in the area of comparative cognitive theory (Buddhism and Western Psychology), as well as comparative examinations of the Buddhist notions of karma with the views of evolutionary biology.