Use of Tense
Literary criticism is conventionally written in the present tense, unless you are referring to an historical event. So "Chaucer wrote The Canterbury Tales", but "In The Canterbury Tales, Chaucer writes about a group of pilgrims on their way to Canterbury". There is nothing theoretically wrong about putting "wrote" in the second example; it's just that it's unconventional. Hence we professors aren't used to it and find it odd. More importantly, we react very badly to essays that narrate events in literature in the past tense, as in the following example:
When Theseus broke up the fight between Palamon and Arcite, he decided to make himself the referee.
Here the use of the present tense makes much more sense. Theseus' intervention isn't a one-off; it happens every time you open the book and read the passage in question. No matter how much we professors try to ignore the effect of the unconventional use of the past tense in contexts like the quote above, it still makes us think that the student has read the Knight's Tale, dashed off an essay, and gone off to watch Sex in the City, never to have another thought about Theseus, Palamon, and Arcite again. How depressing!
There are, of course, some cases when the past tense is appropriate. Consider the following example:
Theseus indulges the two young knights since, like them, he was once a servant of love.
Here the was refers to an event that took place before the event being described. You'll notice that the actual event being described -- Theseus' indulgence -- is still referred to in the present tense.