In his lifelong work at the Department of Philosophy of Addis Ababa University, Sumner initially worked on the written sources of Ethiopian philosophy. It is after the production of multiple volumes on the written sources that he turned to the oral sources. The major ones are contained in three volumes titled, “Oromo Wisdom Literature.” By developing an approach that looked at philosophy in the broader and strict senses Sumner studied the different oral sources of Oromo philosophy. His approach to philosophy was that, while writing is a very important aspect of doing philosophy, this does not, however, mean that oral sources cannot have philosophical content. This is what has been demonstrated by H. Odera Oruka’s sage philosophy. Sumner use...