宗教学
Although he is more well known for his work in Christianity, Walls has also been a significant pioneer in shaping the field of religious studies as it is taught in universities of Scotland. When he first returned to Scotland, Walls taught Ecclesiastical History in the University of Aberdeen in 1966. However, he recognised that the Faculty of Divinity in Aberdeen did not allow for a sufficient global perspective of religion, and founded the Department of Religious studies outside the Faculty of Divinity in 1970.