Present used as continuing action in the past?

Question

In Fabulae Faciles, there is an odd construction using the deponent present apparently as action in the past:

Dum hīc morātur, Herculēs magnum incommodum ex calōre sōlis accipiēbat;

"While he waits here, Hercules received a great inconvience from the heat of the sun..."

So, this sentence is confusing because the action is happening in the past, so why is the present tense of the deponent used? I would have expected the imperfect mōrabātur which would be parallel to accipiebat, but instead we have the present. I know that sometimes, the present tense is used in historical writing to make it seem more exciting, but then why is accipiebat not in the present tense as well? Seems to make no sense.

Answer 1

This is a special exception to the normal tense rules. When dum is used with an ongoing action happening in the past, it's normally followed by the present tense, not the imperfect. The imperfect is allowed too, if you want to put a lot of emphasis on the past-tense-ness of it all, but the present tense is more common.

(Note that this isn't the only time you'll see the present tense with a past meaning: it's sometimes used for vividness in stories, which is called the "historical present". But that's a stylistic choice on the writer's part, not a standard rule of grammar.)