Many writers, students and professionals alike, struggle with the problem of tense shifting. Your writing will be easier to follow if you’re sure to keep your tense consistent.
A verb’s tense lets the reader know when the action is taking place. Is it in the past (ran), present (run), or future (will run)? Since most of the problems occur in the past and present, we’ll leave future tense out of the conversation for now.
In academic writing, the general rule is to use present tense when citing published sources. For example, In her book The Artist’s way, author Julia Cameron writes that…. The signal phrase “author Julia Cameron writes” lets the reader know that information from an outside source is being used. Signal phrases should have present tense verbs.
Most fiction and other narrative writing takes place in the past tense. A narrator is telling a story as it happened. Sometimes, though, a writer will accidentally slip into present tense without realizing it:
I walked down to the edge of the water and dipped my toe in. Suddenly, out of nowhere, Jason grabs my arm and pushes me in the pool!
In the second sentence, the author has slipped from past tense (walked/dipped) into present (grabs/pushes). Most of us do this in casual conversation all the time, so it’s important to be aware of it when we’re writing.
Sometimes, a writer will choose to tell an entire story in the present tense for a sense of immediacy. In any case, it’s important to stick to the tense you’ve started with. Any necessary tense changes should have a clear purpose, and should be done smoothly. Otherwise, your reader will be unnecessarily distracted.