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Is the logician’s ‘if’ what a contract means by ‘if’?

In contract translation, conditionals are where most of my difficulties live.

Arabic has several words that English renders as "if". Classical grammar distinguishes in, for an open possibility; idhā, for something expected to happen; and law, for the counterfactual, what would have been. Hebrew has its own distinctions, with im for the open case and lu for the unreal one. None of these is the logician's truth-functional "if", which only cares whether the parts are true or false.

And contracts add another problem. A clause says: "If the goods are delivered by 1 June, the buyer will pay the full price." Everyone reads it as also meaning that if the goods are not delivered by then, the buyer need not pay the full price. But logically, "if P then Q" says nothing at all about what happens when P is false. The parties hear "if and only if". The text says "if".

So I'd like several answers. Is the logician's conditional the right analysis of "if" in law and contracts, or should we say that ordinary "if" often means "if and only if"? And what do traditions with long legal drafting histories have to say?

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6 answers

  1. Eliana Halpern

    Fellow

    The rabbis noticed exactly your problem. The Mishnah (Kiddushin 3:4) records Rabbi Meir's view that a valid condition must be stated double, a tenai kaful: both what happens if it is fulfilled and what happens if it is not. He derives it from Moses's agreement with the tribes of Gad and Reuben in Numbers 32, which states both sides explicitly. The point is that a bare "if" does not settle the "if not" case. Two thousand years later we still have to tell drafters the same thing.

    Helpful · 2
  2. Hamza Qureshi

    Fellow

    In practice, courts in Lahore read contractual conditions in light of the whole agreement and commercial sense, so they often supply the "only if" the parties obviously meant. But when it matters, it's litigated, and the costs are real. Careful drafters write "if and only if", or state the consequence of non-performance separately. Your Rabbi Meir would have made a good commercial lawyer.

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  3. Derek Hollis

    Fellow

    Programmers live with this. An if without an else does nothing when the condition is false, which is the logician's reading. But users always expect the else-branch to be the "obvious" thing. Most bugs I've chased in specifications come from an unstated else. A contract is a program with a missing else clause and a court as the runtime.

  4. Oskar Nyberg

    Fellow

    Linguists call the inference from "if" to "only if" conditional perfection, and it's usually treated, following Grice's way of thinking, as an invited inference rather than part of the literal meaning. You can cancel it without contradiction: "If you deliver by June you'll be paid in full, and frankly you'll probably be paid in full anyway." So the logician's "if" may still be the meaning, with the "only if" layered on top by context.

    Your Arabic and Hebrew particles are a different matter. They encode the speaker's stance towards whether the condition will or could be met, which the truth-functional conditional ignores entirely.

    Helpful · 1
  5. Layla Sfeir

    Fellow

    On law: the classical grammarians had a lovely description of it, ḥarf imtināʿ li-imtināʿ, the particle of impossibility because of impossibility. The consequent did not happen because the antecedent did not happen. That is a counterfactual described from the inside by grammarians, long before logicians formalised counterfactuals.

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  6. Tal Rosen

    Fellow

    This has given me better vocabulary than I had. For my work: the logical "if" is a floor, not the whole meaning; contracts should spell out the "if not" in the spirit of Rabbi Meir; and when I translate law I'm translating a stance, not a truth-function. "Particle of impossibility because of impossibility" is going on my office wall.

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