An additional difference between truth-conditional vs. use-conditional because clauses is that only the truth-conditional type can be fronted, as illustrated in (15). Sentences (15b–c) would most naturally be interpreted as use-conditional examples if the because clause followed the main clause. But when the because clause is fronted they can only be interpreted as expressing real-world causality, even though this interpretation is somewhat bizarre.
(15) a. Because it’s raining, we can’t go to the beach. [truth-conditional]
b. ⁇ Because I saw Arnold driving a 1995 minivan, he sold his Jaguar. [*use-conditional]
c. ⁇ Because I assume that you came to see her, Mary hasn’t come home yet. [*use-conditional]
Haspelmath (1995) points out that subordinate clauses can often be fronted, but this is typically impossible for co-ordinate clauses. The examples in (16–18) show that a variety of subordinate clauses in English can be fronted. The examples in (19–20) show that this same pattern of fronting is not possible with co-ordinate clauses (though of course it would be possible to reverse the order of the clauses leaving the conjunction in place between them). In light of this observation, the fact that use-conditional because clauses cannot be fronted suggests that they may actually be co-ordinate clauses rather than subordinate clauses.
(16) a. George will give you a ride when you are ready.
b. When you are ready, George will give you a ride.
(17) a. Paul will sing you a song if you ask him nicely.
b. If you ask him nicely, Paul will sing you a song.
(18) a. Ringo draped towels over his snare drum in order to deaden the sound.
b. In order to deaden the sound, Ringo draped towels over his snare drum.
(19) a. George played the sitar and John sang a solo.
b. * And John sang a solo, George played the sitar.
(20) a. Paul asked for tea but the waiter brought coffee.
b. * But the waiter brought coffee, Paul asked for tea.
As we noted above, a pause (comma intonation) is optional before truth-conditional because clauses but obligatory before use-conditional because clauses. (We focus here on the situation where the because clause follows the main clause, since pause is always obligatory when the because clause is fronted.) We can explain this observation if we assume that a pause in this context is an indicator of co-ordinate structure, and that use-conditional functions of because are only possible in co-ordinate structures. Truth-conditional interpretations of because are possible in either co-ordinate or subordinate structures, i.e., with or without a pause. Only the truth-conditional interpretation is possible in subordinate structures (where there is no pause), even when this interpretation is pragmatically unlikely or bizarre (see 9b-c).
Additional support for the hypothesis that a pause is a marker of co-ordination comes from the fact that the scope ambiguities discussed in §18.2 disappear when a pause is inserted between the two clauses. The examples in (21) are not ambiguous, whereas the corresponding examples with no pause are (see 2b, 6, and 7). It is not surprising that an operator in a matrix clause can take scope over a subordinate clause; it would be much less common for an operator in one half of a co-ordinate structure to take scope over the other half.
(21) a. Arthur didn’t marry Susan, because she is rich.
b. Few people admired Churchill, because he joined the trade union.
c. I believed that you love me, because I am gullible.
Interrogative force exhibits similar scope effects: example (22) shows that when a pause is present, the causal relationship cannot be part of what is being questioned. And example (23) shows that a co-ordinate because clause cannot be embedded within a conditional clause.6
(22) Did Mary scold her husband, because he forgot their anniversary? (can only be understood as reason for asking, not as reason for scolding)
(23) #If Mary scolded her husband, because he forgot their anniversary, they will be back on speaking terms in a few days.
In the previous section we used negation, questioning, and embedding within if clauses to argue that Sweetser’s “epistemic” and “speech act” because clauses contribute use-conditional rather than truth-conditional meaning. But if those uses of because are only possible in co-ordinate structures, one might wonder whether perhaps the different behavior of negation, questioning and embedding is due to purely structural factors, and is therefore not semantically relevant?
However, there is at least one test that can be applied to co-ordinate structures, and this test confirms the semantic distinction we argued for in the previous section. This is the challengeability test: the truth of a statement can typically only be challenged on the basis of truth-conditional propositional content. As the following examples show, the truth of a statement which contains a content because clause can be appropriately challenged based on the causal relationship itself, even when the co-ordinate structure is used as in (24). With epistemic and speech act because clauses, however, the truth of the statement can be challenged based on the content of the main clause, but not based on the causal relationship or the content of the because clause (25–26).
(24) A: Mary is leaving her husband, because he refuses to look for a job.
B: That is not true; Mary is leaving her husband because he drinks too much.
(25) A: Mary is at home, because her car is in the driveway.
B1: That is not true. She is not home; she went out on her bicycle.
B2: #That is not true; you know that Mary is home because you just talked with her.
(26) A: There is some pizza in the fridge, because you must be starving.
B1: That is not true; we ate the pizza last night.
B2: #That is not true; you told me about the pizza because want to get rid of it.
To summarize, we have proposed that adverbial clauses introduced by because can occur in two different structural configurations, co-ordinate or subordinate. Co-ordinate because clauses must be separated from the main clause by a pause (comma intonation), but this pause is not allowed before subordinate because clauses (when they follow the main clause). The co-ordinate structure allows either truth-conditional or use-conditional interpretations of because, but only the truth-conditional use is possible in the subordinate structure. Subordinate because clauses can occur within the scope of clausal negation and interrogative force, and can be embedded within conditional clauses; but none of these things is possible with co-ordinate because clauses.
6 The because clause set off by pauses in (23) cannot be interpreted as part of the conditional clause. It could only be interpreted as a parenthetical comment, which in this context produces a very incoherent sentence meaning.
