If there were seven deadly grammar sins, one of them would surely be the sin of doubles. What do I mean by that? Well oftentimes people will use double negatives in a sentence, double prepositions, or double subjects. And sometimes it can alter the meaning of their sentence or make their sentence really clunky. So we want to avoid doubles. I'll give you an example. The other night, I was watching "Saturday Night Live" with my husband, and Justin Timberlake came on. And I said, "That guy can't do no wrong."
Well my husband turned to me, and he said, "First of all, you're married. Second of all, you just committed the sin of a double negative." Let me show you what it looks like. So if we say, "He can't do no wrong," we have two negatives in the sentence. One is the word can't. The positive would be to say, "He can do." The negative is to say, "He can't do." And the other negative in the sentence is to say no, no wrong, as opposed to just wrong. By doing this, by putting a double negative in the sentence, we actually change the meaning to the exact opposite of our intention. What this really mean is that he can't do anything right, and that's not what I intended to say. Now I'll show you what a double preposition looks like. In this sentence, we say, "He jumped off of the stage." Well here we have two prepositions. Prepositions indicate the location of words in relation to one another.
Our two prepositions are "off of." In this case, they don't change the meaning, but they're unnecessary. It would mean the same thing if we just said, "He jumped off the stage." It gives us a more streamlined sentence to drop one of the prepositions. Finally, I'll show you what a double subject looks like. In this sentence, "Justin, he can sing," we have two subjects, Justin and he. The both mean the same thing, and therefore they're both unnecessary. Again, it's much crisper and clearer if we just say, "Justin can sing." So that's a little tip about avoiding the deadly sin of doubles in your writing.