Need help with this specific use of "Should" [duplicate]
Conditionals in English are usually formed by using if with normal word order; but for the three past (subjunctive) forms were, should, and had, it is also possible to express the conditional through subject–auxiliary inversion alone, with no if in the conditional clause.
Does forming conditionals in this manner differ semantically from if-conditionals? Is some aspect of the conditional statement or the conditionality emphasised more in one version than in the other? Or are there differences in how and when they are used? Or are they simply completely interchangeable?
For example:
If I were you, I would try it again
Were I you, I would try it againIf I had seen it, I would have told you
Had I seen it, I would have told youIf you should drink, don’t get behind the wheel
Should you drink, don’t get behind the wheel
The phenomenon mentioned here is often called Conditional Inversion in the linguistic literature. Here's an interesting paper about it.
One difference between Conditional Inversion and if is that inversion is really only possible with those three verbs, as you note, and hence is usually only found with counterfactuals. Another difference is that inversion doesn't work well with the focus adverb only:
- Only if I had thought that he was sick would I have called him.
- *Only had I thought that he was sick would I have called him.
Those are my judgements and the judgements of the authors of the paper I linked to, and my guess is that they are in line with modern usage generally, though it would be good to check. The Iatridou & Embick paper gives some more potential contrasts. Their conclusion is that verb-initial conditional clauses can't be focused, and that "The use of inversion is meant to indicate the fact that the truth of the proposition in the antecedent is old [information]".
A side point is that in the recent history of English this type of inversion was possible with a lot more verbs, including could, would, might and did (Denison 1998: 298-300). This might account for the overall rather formal flavour of these examples, as Greg Lee mentioned in his comment.
Still, in a large number of situations the two constructions are completely interchangeable (for me at least).
Ref: Denison, David. 1998. Syntax. In Suzanne Romaine (ed), The Cambridge Grammar of the English Language, vol. 4: 1776-1997, 292-329. Cambridge: Cambridge University Press.