My rant this week is directed at people who use the term “based on” when they should be using “on the basis of”, which, judging from various things I have read recently, must be an awful lot of people.

“Based on” is adjectival, and therefore attaches itself to the nearest noun, which may not be what the writer intends. “On the basis of”, on the other hand, is adverbial, and hence seeks out the verb. Let’s look at a typical example of the misuse of “based on”:

Based on the current level of interest in flying saucers, the book is expected to be a great success.

This sentence is ambiguous. Strictly speaking, we should interpret the “based on” as applying to the book; so we deduce that it’s a book about the current level of interest in flying saucers. But the writer may have actually meant that it is the expectation of success that is based on the current interest in flying saucers. The correct way of saying this would be

On the basis of the current level of interest in flying saucers, the book is expected to be a great success.

Here, the first half of the sentence, up to the comma, is an adverbial phrase. If we really really want to use “based on”, we must change the last part of the sentence so that it includes a suitable noun for it to attach to:

There is an expectation, based on the current level of interest in flying saucers, that the book will be a great success.

Here, “based on … saucers” is clearly an adjectival phrase which describes the expectation, not the book.

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