Mixed conditional clause type 1-3

Question

I came across the following conditional clause while studying a grammar book published by Oxford:

"If you know London so well, you shouldn't have got so hopelessly lost."

The writer of the book has only briefly mentioned that this is a mixed conditional clause (type 1-3) without giving any further explanation in what situation it can be used. I'm already familiar with two other types of mixed conditional clauses (type 2-3 and type 3-2) and have no problem understanding them but this one is causing me some trouble. I need your help. Thanks.

Answer 1

I urge you stoutly to abjure the Trinity. The n^th-conditional framework is a pedagogic device which has almost nothing to do with how conditional constructions are actually used.

The sort of conditional you instance is categorized by Declerck and Reed^† as an indirect inferential of a sort in which

The verb form of the Q-clause represents Q as counterfactual (=contrary to fact, incompatible with the actual world), so that P, whose form does not normally express counterfactuality, is also interpreted as counterfactual:
[...]

(74) b. If (as you say) he really fought in Vietnam for three years, he would {know / have known} a lot about warfare.

[...]
The counterfactuality of Q—or, more correctly, the speaker’s assumption of the counterfactuality of Q—is signalled by the use of the conditional tense or conditional perfect in the Q-clause. The fact that Q (whether [+q] or [-q]) is thus represented as false in the actual world forces the hearer to infer that P (which leads to Q) must also be counterfactual, although its verb form does not represent it as such: for the sake of the argument, the speaker purports to represent P as ‘closed’ (-assumed to be true, as is claimed or suggested in the previous context), but then she makes it clear that this interpretation must be reconsidered.

N^th-conditionals, as they are typically taught, are actualization conditionals, “If P happens, Q happens”: actualization of P causes or triggers the actualization of Q, or at least provides a relevant occasion for the utterance of Q. These conditionals require a sequence of eventualities.

But inferential conditionals present virtually no constraint on the tenses and modes of the verbs. Inferential conditionals are not concerned with the actualization of eventualities but with the truth of propositions: (“If P is true, Q is true”). A proposition may be cast in any tense or mode, but the inference from one proposition to another is always present-tense, although that is rarely made explicit.

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^† Conditionals: A Comprehensive Empirical Analysis, 2001, 3.6.2, 44-45. The authors’ terminology rests on the traditional conditional template “If P, Q”; they employ P-clause for the condition (IF) clause and Q-clause for the consequence (THEN) clause. Lower-case abbreviations [p], [q] represent the propositions expressed in the clauses P and Q, with '+' and '-' representing positive and negative assertions.