The only way is if~

conditionalsgrammaticality

I have never gotten to listen to one of those Parental Warning CDs, because Mom and Dad never let me buy them at the mall. So I realized the only way I was gonna get a chance to listen to Rodrick's CD was if I snuck it out of the house. (from Diary of a Wimpy Kid by Jeff Kinney)

The only way I was gonna get a chance to listen to Rodrick's CD was if I snuck it out of the house.

The use of "if" above is grammatical and correct? As far as I know, "If" has two uses.

  1. used in conditional clauses as adverbial clauses
  2. used in interrogative clauses as nominal clauses(in this case, if the clause is used as an object, "if" can be replaced by "whether". More importantly, "if" clause cannot be in a 'subject complement' position)

I am confused about which category the "if" above falls under. 1) or 2) or nothing? The "if" clause above is a nominal clause, but at the same time, has a conditional meaning. Also, it is in a subject complement position.

Is this use of "if" grammatical? correct? idiomatic? or just colloquial and informal?

Best Answer

This construction is fairly common in print. Some examples appear to be formal writing, and I see nothing wrong with them:

But how can all of 5.1-5.5 be true? The only way is if the following is also true: Commonsense Consequentialism (2011) p.130

The only way this will find concrete, tangible, and long-term expression in society and community—in our world—is if you learn how to work with others and form a society—a guild, a school, a hospital... Institutional Intelligence (2017) p.6-7.

In the first example, one could say ...is by accepting the following as true, but the point may be that the "following" is not true (and 5.1-5.5 are not all true as a consequence). The if construction does a better job in that case.

In the second example, one could replace ...is if you learn how ... with ...is by learning how or ...is to learn how... But they are not exactly the same -- the conditionality feels weaker.

The only way the party will be a success is if Susan comes can't be transformed with ...to have Susan come or ....by having Susan come. They both imply Susan hasn't been invited. ...to ensure/by ensuring Susan comes do imply she's been invited, but they also have a different meaning.