What tense to use in arts and humanities papers?
Verb tense often distinguishes a paper in the humanities from one in the
natural and social sciences.

Generally you would write in the present tense in the humanities (e.g. John Doe explains) and you would use the past tense in a humanities paper only for reporting historical events.

The UNC Writing Centre have a good webpage with examples that explain the three types of verb tenses (present simple, past simple, and present perfect) that they say account for approximately 80% of the verb tense use in academic writing.