Q: Is the word “of” necessary in these two examples: “She closed all of the blinds” and “The bull runs with all of his might”?
A: The preposition “of” is optional in both examples. The sentences would be good English with or without it.
It seems to us, though, that your first example (“She closed all of the blinds”) may be a bit more emphatic with “of.”
And your second (“The bull runs with all of his might”) may be a bit more idiomatic without it, but there’s nothing wrong with using “of” here.
In fact, some googling suggests that both versions of the second example (“all his might” and “all of his might”) are quite common, though the one without the preposition is more popular.
The scorecard as of this writing: “all his might,” 3.95 million results; “all of his might,” 1.8 million.
Although the use of the preposition is optional in your examples, it’s sometimes a no-no.
Pat writes about optional as well as undesirable uses in the new third edition of her grammar and usage book Woe Is I.
The following passage from Woe Is I buries the old misconception that “of” should always be deleted from the phrases “all of” and “both of”:
“Some members of the Redundancy Police think of is undesirable in the phrases all of and both of, except in front of a pronoun (all of me, both of them, etc.). They frown on sentences like Both of the thieves spent all of the money, and would prefer Both the thieves spent all the money.
“Either way is correct. There’s no law against keeping of, but by all means drop it if you want to. You can’t please all of the people all the time.” (Page 220 in the paperback.)
Another passage from the book deals with the undesirable use of the preposition in these examples: “Paulie says his new TV fell off of a truck. The missing warranty is not that big of a problem.”
Pat’s advice to readers: “Whack the of: Paulie says his new TV fell off a truck. The missing warranty is not that big a problem.” (Page 127.)
We’ve also written a blog item about the unnecessary “of” in expressions like “not that big of a deal.”
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