Parallelism is recurrent syntactical similarity. Several parts of a sentence or several sentences are expressed similarly to show that the ideas in the parts or sentences are equal in importance. Parallelism also adds balance and rhythm and, most importantly, clarity to the sentence.
Any sentence elements can be paralleled, any number of times (though, of course, excess quickly becomes ridiculous). You might choose parallel subjects with parallel modifiers attached to them:
- Ferocious dragons breathing fire and wicked sorcerers casting their spells do their harm by night in the forest of Darkness.
Or parallel verbs and adverbs:
- I have always sought but seldom obtained a parking space near the door.
- Quickly and happily he walked around the corner to buy the book.
Or parallel verbs and direct objects:
- He liked to eat watermelon and to avoid grapefruit.
Or just the objects:
- This wealthy car collector owns three pastel Cadillacs, two gold Rolls Royces, and ten assorted Mercedes.
Or parallel prepositional phrases:
- He found it difficult to vote for an ideal truth but against his own self interest.
- The pilot walked down the aisle, through the door, and into the cockpit, singing "Up, Up, and Away."
Notice how paralleling rather long subordinate clauses helps you to hold the whole sentence clearly in your head:
- These critics--who point out the beauties of style and ideas, who discover the faults of false constructions, and who discuss the application of the rules--usually help a lot in engendering an understanding of the writer's essay.
- When, at the conclusion of a prolonged episode of agonizing thought, you decide to buy this car; when, after a hundred frantic sessions of begging stonefaced bankers for the money, you can obtain sufficient funds; and when, after two more years of impatience and frustration, you finally get a driver's license, then come see me and we will talk about a deal.
- After you corner the market in Brazilian coffee futures, but before you manipulate the price through the ceiling, sit down and have a cup of coffee with me (while I can still afford it).
It is also possible to parallel participial, infinitive, and gerund phrases:
- He left the engine on, idling erratically and heating rapidly.
- To think accurately and to write precisely are interrelated goals.
- She liked sneaking up to Ted and putting the ice cream down his back, because he was so cool about it.
In practice some combination of parts of speech or sentence elements is used to form a statement, depending as always on what you have to say. In addition, the parallelism, while it normally should be pretty close, does not have to be exact in its syntactical similarity. For example, you might write,
- He ran up to the bookshelves, grabbed a chair standing nearby, stepped painfully on his tiptoes, and pulled the fifty-pound volume on top of him, crushing his ribs and impressing him with the power of knowledge.
Here are some other examples of parallelism:
- I shall never envy the honors which wit and learning obtain in any other cause, if I can be numbered among the writers who have given ardor to virtue, and confidence to truth. --Samuel Johnson
- They had great skill in optics, and had instructed him to see faults in others, and beauties in himself, that could be discovered by nobody else. . . . --Alexander Pope
- For the end of a theoretical science is truth, but the end of a practical science is performance. --Aristotle
