precondition + for / of / to - what's the difference?
In cases where usage might be a bit uncertain, it's good to remember that language is a living thing and that the uncertainty may reflect the fact that usage has been changing.
A tool that I have come to love when faced with this sort of puzzle is Google's N-Gram. See how it's used in this particular case at:
You can see that up until about 1960, "of" was the preferred preposition, but in the following fifty years it's become pretty soundly beat out by "for."
If you change the date conditions you can see where this trend really took off:
Evidently either the stock market crash or perhaps the early stirrings of unrest in Germany somehow triggered a sudden rise in the use of "for." Why? I don't know... perhaps the explanation is as simple as a single head editor at the NY Times declaring that "for" was the "proper" preposition to use and the usage then began to build.
ADDENDUM: I discovered N-Grams while investigating the origin of the statements "Kissing a smoker is like licking an ashtray." or telling someone they "smell like an ashtray." I was curious as to what degree this was a "natural" observation that people had expressed for many years or if it was artificially created as part of a wider movement to create prejudice. N-Gram is limited to four words in a phrase for the most part so I created the following for the test:
(can't link as I'm still a bit disreputable { unreputable? :> } so I'll just note you should enter the two phrases "like licking an ashtray" and "smell like an ashtray" into the N-Gram. Remember: do NOT put quotes around the phrases -- just commas to separate them!)
As you can see, the concept is a relatively recent social construct, appearing only after 1975's "World Conference on Smoking and Health" decided to shift the focus of the stalled antismoking movement over to denormalizing smokers as a path toward what they eventually began calling "The Endgame." As George Orwell once noted: "As thought corrupts language, so can language corrupt thought." We see the game played out here in the US every four years as well as presidential candidates search for the perfect soundbite or image to portray their opposition as corrupt, evil, or simply silly or stupid.
Have fun with N-Gram! It's WONDERFULLY useful tool!
- MJM
In every day use I change the preposition depending on how I use or refer to the object of the sentence (the exam), for example:
a precondition of - The text is a precondition of the exam (object context, talking about the exam)
a precondition for - The text is a precondition for taking the exam (action context, doing something to the exam)
a precondition to - The text needs to be read before hand as it is a precondition to examinations (time context, referring to an action in the future)