There are no hard and fast rules for how many sources are considered sufficient as assignments are so varied. If your assignment were to analyze “Language, Epistemology, and Mysticism” by Steven T. Katz , his article might be your only source or it may be necessary to consult secondary literature on this important essay. In most circumstances, you will need multiple sources, including both primary and secondary sources.
Be particularly mindful that the secondary sources you are using to analyze your topic reflect current scholarship and are not all from the 1970’s. If there is no recent secondary literature available, you probably will want to modify your topic to reflect a more current issue.