Fallacies

   "If I can do it, you can do it." It ain't necessarily so. Picture Shaquille O'Neal telling Danny DeVito that he too can succeed in professional basketball.

   Anyone can be taught to play the piano, but there is only one Dave Brubeck.

   "Those who can, do. Those who can't, teach."
   As well say, "Those who can, play. Those who can't, coach."
   Or, "Those who can, play. Those who can't, conduct."

   "Verbs must always agree with nouns."
   True enough, but a noun is not always a single word. It could be an entire phrase. Consider the following, which appeared in a New York Times story about student loan defaults: "Only a small fraction of defaulters even tries" to get the loan amount reduced or forgiven. The editor or writer decided that the ruling noun is "fraction," and used the singular verb "tries." But that clashes with the nearest noun, "defaulters," who are clearly numerous people, and this plural noun requires the plural verb "try." Moreover, it's not at all clear that a "fraction are people." Or is it "fraction is people"?
   There are several ways to resolve the problem. One is to consider that the governing noun is not the single word "fraction," but the entire noun phrase, "fraction of defaulters." Another is to consider that the verb should agree with the nearest noun, in this case, "defaulters." Still another is to rewrite the sentence, such that any doubt is eliminated, thereby following the Samurai Rim Man's mantra, "When in doubt, rephrase."
   In any case, the construction "defaulters ... tries" compels the reader to stop and wonder which verb usage is appropriate. The idea of good writing is induce continued reading, not to force pauses to ponder usage.
   In short, collective nouns can take either a singular or a plural verb, depending on whether its members are acting as a group or as many individuals.