Communicative foundation

Condition is a relation between two propositions ↴S and S↴ none of which is asserted in the sense in which the proposition of a simple declarative sentence is asserted. The speaker feigns a situation in which ↴S, called protasis, is real, and asserts that in this situation S↴, called apodosis, is real, too. The speaker's assumption is based on an agreement with the hearer, which may be made explicit (s. below), but otherwise is just a semantic feature of the construction. The logical dependency between the two propositions is based on some unexpressed cognitive or communicative connection between them, typically a causal one.

Positing the protasis as a component of a “possible world” and asserting the apodosis as something valid in this world are two separate operations which jointly constitute a conditional sentence. In this perspective, the conditional sentence reflects a conversational exchange:

1. Speaker asks hearer to (temporarily) accept ↴S as valid in the universe of discourse.
2. Presupposing this, speaker proceeds to the consequent S↴.

Such conversational exchanges do occur as the maximally explicit form of a conditional construction, like this exchange between interlocutors A and B:

• A: Let us assume that ↴S.
• B: Okay.
• A: Then S↴.

A conditional construction in the form of a complex sentence is, of course, uttered by one speaker, who takes the hearer's consent to the protasis for granted. Consequently, the conditional sentence may be considered as the grammaticalization of the structure of such a conversational exchange.

Unlike disjunction, the protasis and the apodosis of a conditional are not principally in a paradigmatic relation. They may, however, be in such a relation. In that case, the conditional ‘if not ↴S, S↴’ may take the form of ‘if not ab, then ac’ (.a). In such a case, a conditional may be replaced by a disjunction ‘ab or ac’ (.b). In conditionals that have this semantic form, reduction processes may apply that are similar to those found in coordinative junction. This may result in a complex clause of the form ‘a (if not b, then c)’ (.c; s. Mauri 2008).

Plain conditional

Status of the protasis

This concerns presuppositions concerning the fictivity or invalidity of the protasis (cf. Lehmann 1973, ch. 5).

1. A reality-based (traditionally: “real”) condition is unmarked in this respect and may therefore be assumed on the basis of a state-of-affairs that has the status of ‘real’ in the universe of discourse ().– A variant of this is the conditionally-downtoned causal connection: .
2. A fictitious (traditionally: “potential”) condition is marked by a presupposition that it has nothing to do with anything taken as real, as being just a thought-experiment ().
3. A counterfactual (traditionally: “irreal”) condition is marked by a presupposition that the logical opposite of its proposition is taken as real ().

This parameter must be cross-classified with tense and aspect distinctions.

These and similar distinctions may or may not be made at the level of grammatical structure of the given language.

Nature of the interpropositional relation

1. cognitive relation: causal etc.: ,
2. communicative relation:
   • interpretative conditional:
   • speech-act related: .

Concessive conditional

In a concessive conditional of the form ‘even if ↴S, S↴’ (), the speaker presupposes that the universe of discourse contains a conditional ‘if ↴S, not S↴’ () and denies this conditional; i.e. he asserts S↴ whatever the status of ↴S.

Subdivisions of the concessive conditional are as for the plain conditional.

The concessive conditional bears an analogy to the plain concessive relation, treated elsewhere. The difference from the latter is that a concessive conditional does not assert or presuppose (the reality of) the protasis (↴S).

Coding strategies

For most interpropositional relations, asyndetic parataxis means that they are not coded and can only be inferred. This appears to be different for the conditional relation. The universal default order is ‘protasis - apodosis’. If this order is present and the intonation contour is ‘protasis = left-dislocated topic, apodosis = comment’, with the appropriate rising intonation at the end of the protasis, then this sufficiently codes a conditional relation in several languages. Moreover, this construction is even found in writing, where there is no intonation contour. Thus in the street sign .

The meaning is ‘If the bridge is open, turn the motor off.’