Q: I’m confused about the tense of verbs in “if only” sentences. For example: “The world would be better if only people would understand each other.” Does this sound OK to you?
A: The phrase “if only” is used in this hypothetical way “to express a strong wish that things could be different,” according to Cambridge Dictionaries Online.
When used to discuss a wish about the present, Cambridge says, the “if only” part of the sentence should be in the past tense.
So your example, according to the dictionary, should read: “The world would be better if only people understood each other.”
When used to discuss a wish about the past, Cambridge says, the “if only” part should be in the past perfect.
Example: “The world would have been better if only people had understood each other.”
And to discuss a wish about the future or to contrast how things are with how we’d like them to be, the “if only” part should be in the conditional.
Example: “The world could be a better place if only people would understand each other.”
We’ll add that in the US, “if only” is used with the subjunctive to express a wish about the present. However, this is obvious only when the verb is “be.”
Example: “If only the world were better, people would understand each other.” (In Britain, where the subjunctive is on the decline, “was” would generally be used.)
The Cambridge entry for “if only” is borrowed from English Grammar Today, a Cambridge University Press guide written by Ronald Carter, Michael McCarthy, Geraldine Mark, and Anne O’Keeffe.
The online Oxford Dictionaries defines this wishful use of “if only” somewhat differently (the example expresses a wish about the past): “Used to express a wish, especially regretfully: if only I had listened to you.”
Oxford gives this example of “if only” used in a more complex construction: “Most salmon anglers have a wish list of places they would love to fish if only they could afford it.”
Oxford notes that the phrase “if only” has an additional meaning: “Even if for no other reason than: Willy would have to tell George more, if only to keep him from pestering.”
The dictionary has several other examples of the usage, including this one about Kingsley Amis’s novel Lucky Jim and the poet Philip Larkin:
“It has also prompted me to get Lucky Jim out of the library if only for the shallow reason that Larkin is the dedicatee.”
Finally, an “if” sentence never needs more than one “would,” as in this common error: “If I would have shown him, he would have believed me.” We wrote a post a few years ago about how to juggle two different tenses in one “if” sentence.
In short, here’s the drill:
(1) When the first verb is in the simple present, the second is in the simple future: “If I show him, he will believe me.”
(2) When the first verb is in the simple past, the second is in the simple conditional: “If I showed him, he would believe me.”
(3) When the first verb is in the past perfect, the second is in the conditional perfect: “If I had shown him, he would have believed me.”