Parallelism might sound like some weird cult, but it’s merely good grammar.
Sometimes part of a sentence is compound, such as when you write two verbs for one subject. Tommy jumped and ran. No problem so far, right? Those verbs are both third person singular past indicative. (Remember all that from seventh grade?)
Even if you don’t remember all that, the point is that both verbs are that way. That’s parallelism. The rule in English is that when you have a compound part of a sentence, the parts of the compound construction should be parallel. You wouldn’t say, “Tommy jumped and running.”
When the sentences get longer, you have to be more careful, because the lack of parallelism is easier to miss. Here’s a sentence from a professional writer whose work I enjoy. He’s writing about himself, in the third person, and I suppose we can forgive him for this small solecism—he’s an astronomer.
“He is a skeptic, and fights misuses of science as well as praising the wonder of real science.”
So—do you see the compound verb? fights, and whoops! praising. He should get rid of the excessive “as well as” and use plain old “and.” then the parallelism is easier to see and get right:
“He is a skeptic, and fights misuses of science and praises the wonder of real science.”
Sometimes you can play fast and loose with parallelism, but when you want to write most clearly, keep it simple. Stay parallel.
See if you can spot some misplaced verb forms. Share one with us in the comments.