1 Introduction

In this paper, we investigate the effects of coordination on the status of multiple sluicing constructions in English. We build on the observation that coordination sometimes improves the status of constructions that are ungrammatical without coordination. This is, for example, what happens in multiple wh-questions: the ungrammatical sequence of two fronted wh-phrases in (1a) becomes grammatical when the two wh-phrases are coordinated, as shown in (1b) (Browne 1972; Kazenin 2002; Whitman 2002; 2004; Gračanin-Yuksek 2007; Gribanova 2009; Scott 2012; Citko and Gračanin-Yuksek 2013; 2016, among many others):

Similarly, the ungrammatical sequence of a complementizer followed by a wh-phrase in (2a) becomes grammatical when a conjunction separates them, as shown in (2b) (Giannakidou and Merchant 1998; Citko and Gračanin-Yuksek 2017).

We focus on a similar contrast, involving multiple sluicing constructions. In English, multiple sluicing is quite restricted: the ungrammatical multiple sluicing example in (3a) improves when the two wh-phrases are coordinated, as shown in (3b) (Bolinger 1978; Hoyt and Teodorescu 2012).¹²

We examine possible sources for coordinated sluices, and show that coordinated sluices like (3b) above cannot be derived from multiple sluices in (3a). We also show that they cannot be derived from coordinated wh-questions or coordinated clefts, illustrated in (4a–b), respectively.

We propose instead that coordinated sluices involve coordination of two CPs, with a single wh-phrase sluiced in each, as shown in (5).

We proceed as follows. In Section 2, we investigate coordinated wh-questions as a possible source for coordinated sluices and show that deriving coordinated sluices from coordinated wh-questions makes an incorrect prediction for English that the two should be subject to the same restrictions. In Sections 3 and 4, we argue against deriving coordinated sluicing from multiple sluicing and coordinated clefts, respectively. In Section 5, we present our proposal, and in Section 6, we address the question of why coordinated wh-questions and coordinated sluices cannot share the same underlying structure. Section 7 is the conclusion.

2 Coordinated wh-questions as possible source for coordinated sluicing

2.1 Background on English CWHs

Coordinated Wh-Questions (henceforth CWHs) are questions in which two wh-phrases, not necessarily of the same category, appear conjoined in a left-peripheral position, as shown in (6a–b). The grammaticality of (6a) is not surprising given that it involves coordination of two Adverbial Phrases (so they could be part of a larger Adverbial Phrase), but in (6b) coordination would have to target a DP and an AdvP, in violation of the Law of the Coordination of Likes (Williams 1981). This has led to alternative analyses for CWHs, on which coordination involves larger (clausal) constituents, or which regard the fact that coordinated constituents are wh-phrases as sufficient for the purposes of evaluating “likeness” (see Gračanin-Yuksek 2017 for an overview of existing approaches to CWHs).

(6)	a.	[AdvP When] and [AdvP where] were you born?
	b.	[DP Who] and [AdvP when] did you teach?

English CWHs have been shown to be subject to a number of restrictions (discussed by Browne 1972; Kazenin 2002; Whitman 2002; 2004; Gračanin-Yuksek 2007; Gribanova 2009; Scott 2012; Citko 2013; Citko and Gračanin-Yuksek 2013; 2016, among many others). In order to capture these restrictions, Gračanin-Yuksek (2007) proposes that English CWHs have the structure in (7b), which she dubs a bi-clausal non-bulk sharing structure.³ It is bi-clausal because coordination is at the CP level, it is sharing because the two CPs share lexical material due to the multidominant nature of the structure (in this particular case, the two CPs share everything except for the wh-phrases). And it is non-bulk sharing because multiple individual nodes are being shared (rather than a larger chunk of structure being shared in bulk).

(7)	a.	What and when did you eat?
	b.

This structure captures a number of restrictions on English CWHs. The first one concerns the ban on coordinating two wh-arguments, illustrated in (8a). This example is ungrammatical for the same reason (8b) is ungrammatical. The verb put requires two VP internal arguments, but since according to the structure in (7b) it has only one per conjunct, its selectional requirements are not satisfied in either conjunct.

(8)	a.	*What and where did you put?
	b.	*What did you put and where did you put?

The second restriction concerns CWHs with obligatorily transitive verbs like buy. Such CWHs are ungrammatical if one of the wh-phrases is an adjunct and the other one a direct object, as shown in (9a), whose ungrammaticality also reduces to that of (9b).

(9)	Obligatorily transitive V; wh-DO & wh-adjunct
	a.	*What and when did you buy?
	b.	*What did you buy and when did you buy?

In this respect (9a) contrasts with (10a); instead of the obligatorily transitive verb buy, (10a) has the optionally transitive verb eat, which can be interpreted intransitively in the conjunct that is missing the direct object.

(10)	Optionally transitive V; wh-DO & wh-adjunct
	a.	What and when did you eat?
	b.	What did you eat and when did you eat?

The third restriction concerns CWHs in which one of the coordinated wh-phrases is a subject, such as the one in (11a). This example is ungrammatical because in English all finite clauses require an overt subject, due to the EPP requirement (Chomsky 1981). In (11a), however, since the subject is one of the wh-phrases, it is only part of the first conjunct, but not the second one, as shown in (11b).

(11)	a.	*Who and when sang?
	b.	*Who sang and when sang?

Finally, the structure in (7b) captures the interpretation of CWHs; they are interpreted as two coordinated CPs with a single wh-pronoun in each CP, as we would expect given this structure. This is most obvious in CWHs in which one of the coordinated wh-phrases is a direct object, and the other one is an adjunct, such as the one in (12a). This example can have the so-called at-all reading, paraphrased in (12b), on which the wh-object is not part of the interpretation of the question introduced by the wh-adjunct. Since the wh-object is not part of the conjunct introduced by the wh-adjunct, the verb ate in the where-conjunct is interpreted intransitively, giving rise to the at-all reading. The at-all reading contrasts with the so-called it reading, paraphrased in (12c), on which the direct object is present in both conjuncts for interpretive purposes.⁴

(12)	a.	I know what and where you ate.
	b.	At-all reading
		I know what you ate and where you ate at all.
	c.	It reading
		%I know what you ate and where you ate it/the thing you ate.

With this background on CWHs (and the structure in (7b)) in mind, we turn to the question of whether coordinated sluices can be derived from coordinated wh-questions. This is the focus of the next section.

2.2 Against coordinated wh-questions as the source of coordinated sluicing

If coordinated sluices were derived from coordinated wh-questions, the only difference between the structure of CWHs, given in (13b), and the structure of coordinated sluices, given in (14b), would be that in coordinated sluicing, TPs in the two conjuncts undergo ellipsis (indicated in (14b) by shadowing and dotted lines).⁵

(13)	a.	I don’t remember what or where John sang.
	b.

(14)	a.	I know John sang something at some event, but I don’t remember what or where.
	b.	…but I don’t remember

In the previous section, we reviewed the restrictions on English CWHs and showed how these restrictions follow from the structure in (13b). Assimilating coordinated sluices to CWHs predicts that coordinated sluices should be subject to the same restrictions. This is not what we find: coordinated sluices are not subject to the same restrictions as coordinated wh-questions. First, coordination of obligatory arguments is impossible in CWHs, but possible in coordinated sluicing, as shown in (15a–b).

(15)	a.	Coordinated Wh-Questions
		*Do you know what and to whom John gave?
	b.	Coordinated Sluicing
		I heard that John gave something to someone. Do you know what and to whom?

Second, in CWHs involving obligatorily transitive verbs, coordination of a wh-object with a wh-adjunct is impossible, as shown in (16a). No such restriction holds of coordinated sluicing, as shown in (16b).

(16)	a.	Coordinated Wh-Questions
		*Do you know what or when John bought?
	b.	Coordinated Sluicing
		I know John bought something sometime last week, but I don’t remember what or when.

Third, coordination cannot involve a subject wh-phrase in CWHs, but it can in coordinated sluicing, as shown by the contrast between (17a) and (17b).

(17)	a.	Coordinated Wh-Questions
		*Do you know who and when ate?
	b.	Coordinated Sluicing
		I know that someone ate at some point. Can you tell me who and when?

Coordinated sluices also differ from CWHs with respect to their interpretation. We saw in (12) above that English CWHs have at-all readings. Another example of this is given in (18). By contrast, coordinated sluices do not have at-all readings, and only allow it readings, as shown in (19). This indicates that the wh-phrase introducing the first conjunct (what in our example) in a coordinated sluice is also interpreted in the second conjunct.

(18)	a.	Coordinated Wh-Questions
		What and where did John sing?
	b.	At-all reading
		What did John sing and where did John sing at all?

(19)	a.	Coordinated Sluicing
		I heard that John sang something, but I forgot what and where.
	b.	At-all reading
		#…but I forgot what John sang and where he sang at all.
	c.	It reading
		…but I forgot what John sang and where he sang it.

These differences between CWHs and coordinated sluices lead us to conclude that coordinated sluices are not derived from CWHs. We have not said anything yet about why this should be the case; we will discuss this question in Section 6. First though, we turn to multiple sluicing as a possible source for coordinated sluicing.

3 Multiple sluicing as possible source for coordinated sluicing

3.1 Background on multiple sluicing

Multiple sluicing in English has been analyzed in various ways (see Vicente 2018 for an overview). On one analysis (Nishigauchi 1998; Lasnik 2007; 2014), the first wh-phrase in a multiple sluicing configuration moves leftwards to [Spec CP], while the second one is extraposed/moved rightwards to an adjoined position, as shown schematically in (20b).

(20)	a.	Lasnik (2014: 9)
		Someone was talking (yesterday) to someone, but I don’t know who to who.
	b.	…but I don’t know whoi [ti was talking tj (yesterday)] to whoj.

If (20b) is the correct analysis of multiple sluicing, could coordinated sluicing be derived in an analogous way, and, if so, what would such a derivation look like? One possible structure is given in (21b); the first wh-phrase moves to [Spec CP], and the second wh-phrase moves in a sidewards manner (Nunes 2001; 2004) and merges with the conjunction head. The result, however, violates the Law of the Coordination of Likes (Williams 1981): it involves coordination of a CP with a PP. The two conjuncts are not both wh-phrases nor are they similar in any other respects, so it is hard to imagine how a violation of the Law of the Coordination of Likes might be avoided in this structure.

(21)	a.	Someone was talking (yesterday) to someone, but I don’t know who or to whom.
	b.	…but I don’t know

Another prominent analysis of multiple sluicing in English involves multiple leftward movement of both wh-phrases to [Spec CP] (Merchant 2001; Richards 2001; 2010; Park and Kang 2007; Abels and Dayal 2017a; b, among others), as shown in (22b).

(22)	a.	Park and Kang (2007: 396)
		?Mary showed something to someone, but I don’t know exactly what to whom.
	b.	…but I don’t know exactly [CP whati [C’ to whomj [TP Mary showed ti tj]]]

What is unusual about this derivation for a language like English is that both wh-phrases undergo overt wh-fronting: multiple overt wh-fronting in English is exceptionally allowed in multiple sluicing because the deletion of the TP removes the violation induced by the pronunciation of the highest copy of the second wh-phrase. For Abels and Dayal, after deletion removes lower copies of both wh-phrases from the structure, the remaining copies count as simultaneously highest and lowest. Thus, it is possible to characterize the examples in (22a–b) as involving the pronunciation of the highest copy of what and the lowest copy of to whom.⁶

3.2 Against multiple sluicing as the source of coordinated sluicing

If coordinated sluices were derived from multiple sluices and if multiple sluices have the structure in (22b), coordinated sluices would presumably involve sideward movement of wh-phrases to form a Coordination Phrase in [Spec CP] (Zhang 2007; 2010), followed by the deletion of the TP in which the wh-phrases originated, as shown in (23b).

(23)	a.	?Mary showed something to someone, but I don’t know exactly what or to whom.
	b.	…but I don’t know exactly

However, there are sufficient differences between multiple sluicing and coordinated sluicing to argue against deriving coordinated sluicing from multiple sluicing. We turn to these differences next.

The first one involves the so-called clause-mate condition. Multiple sluicing crosslinguistically is well-known to be subject to this condition, which requires all wh-remnants in a multiple sluicing configuration to originate in the same finite clause (see Takahashi 1994; Nishigauchi 1998; Merchant 2001; Marušič and Žaucer 2013; Lasnik 2014; Citko to appear, among others). This is shown in (24a–b).⁷

(24)	a.	Lasnik (2014: 6)
		*One of the students said that Mary spoke to one of the professors, but I don’t know
		[which studenti to which professorj [ti said [that Mary spoke tj]].
	b.	Abels and Dayal (2017a: 25)
		*Some linguist was upset because Harry spoke to some philosopher]] but Bill doesn’t know
		[which linguisti which philosopherj [ti was upset [because Harry spoke to tj]].

Coordinated sluicing, however, is not subject to this condition (Abels and Dayal 2017a), as shown by the grammatical status of parallel coordinated sluicing examples in (25a–b).

(25)	a.	[One of the students said [that Mary spoke to one of the professors]], but I don’t know which student or to which professor.
	b.	Adapted from Abels and Dayal (2017a: 25)
		[Some linguist was upset [because Harry spoke to some philosopher]] but Bill doesn’t know which linguist and which philosopher.

The second difference concerns restrictions on wh-remnants. Multiple sluicing is marginal at best if both wh-remnants are simplex wh-DPs such as who or what, and improves considerably (at least for some speakers) if one wh-phrase is either a PP (Lasnik 2014; Abels and Dayal 2017a; b; Kotek and Barros 2018; Cortés Rodríguez 2019), as shown in (26a–b), or a which wh-phrase, as shown in (27a–b).⁸

(26)	Hoyt and Teodorescu (2012: 86)
	a.	*John gave someone something, and I want to know who what.
	b.	?John gave something to someone, but I don’t know what to whom.

(27)	a.	Park and Kang (2007: 396)
		?*Someone saw something, but I can’t remember who what.
	b.	Kotek and Barros (2018: 799)
		Every boy likes some girl, but I don’t know which boy which girl.

Coordination of simplex wh-DPs, by contrast, is perfectly fine in coordinated sluicing, as (28) shows.

(28)	Hoyt and Teodorescu (2012: 86, crediting Richards 1997)
	John gave someone something, and I want to know who and what.

Another difference concerns interpretation; the interpretation of coordinated sluicing is different from the interpretation of multiple sluicing. Abels and Dayal (2017a: 24) note that multiple sluicing can in principle either have a single-pair (SP) or a pair-list (PL) reading, and that the readings of the sluice are disambiguated by the readings of the antecedent.⁹

(29)	Abels and Dayal (2017a: 24)
	a.	Single-Pair Reading
		Some student has published on some topic, but I couldn’t tell you which student on which topic.
	b.	Pair-List Reading
		Every student has published on some topic, but I couldn’t tell you which student on which topic.

Coordinated sluices, however, only allow single-pair readings, as noted by Abels and Dayal (2017a) (also by Gribanova 2009 for Russian, who builds on Grebenyova’s 2004; 2006 work on multiple sluicing). This is indicated by the infelicity of the sluice in (30b), whose antecedent forces a pair-list interpretation.

(30)	a.	Single-Pair Reading
		Some student has published on some topic, but I forgot which student and on which topic.
	b.	Pair-List Reading
		#Every student has published on some topic, but I forgot which student and on which topic.

The last difference between coordinated sluices and multiple sluices involves swiping (Sluiced Wh-phrase Inversion with Prepositions In Northern Germanic) (we thank Anikó Lipták for bringing this fact to our attention). The paradigm in (31a–e), due to Richards (2001), shows that in a multiple sluicing configuration, only the first wh-PP remnant can undergo swiping. This is shown by the grammaticality of (31a). All the other logically possible swiping options are out: in (31b) and (31c) the second PP is swiped, and in (31d-e) both are.¹⁰

(31)	Richards (2001: 139)
	I know John was talking with somebody about something,
	a.	…but I don’t know who with about what.
	b.	*…but I don’t know with who what about.
	c.	*…but I don’t know what with who about.
	d.	*…but I don’t know who with what about.
	e.	*…but I don’t know who what with about.

Coordinated sluices are not subject to this restriction, as shown in (32a–c).

(32)	I know John was talking with somebody about something,
	a.	…but I don’t know who with or about what.
	b.	…but I don’t know with who or what about.
	c.	…but I don’t know who with or what about.

These differences between multiple sluicing and coordinated sluicing lead us to conclude that coordinated sluicing is not derived from multiple sluicing.

4 Coordinated clefts as possible source for coordinated sluices

On some accounts, sluicing can be derived from non-isomorphic pre-sluice sources (i.e., short sources, predicative sources, cleft sources) (Erteschik-Shir 1973; Merchant 2001; Marušič and Žaucer 2013; Barros, Elliott and Thoms 2014; 2015; Vicente 2018, among others). In more concrete terms, this means that the source of the sluice in (33) is the “short” string in (33b) or the cleft string in (33c), rather than the isomorphic string in (33a) containing an island. Since neither (33b) nor (33c) involves an island, the availability of such short sources is one way to derive the lack of island effects in sluicing.¹¹

Abels and Dayal (2017a: 25) suggest that coordinated sluices, like the one in (34a), “are derived from a different pre-sluice”, indicated by their cleft source and/or predicative source paraphrases in (34b).

In this section, we focus on cleft sources and the question of whether coordinated sluices in general can be derived from coordinated clefts along the lines schematized in (35).

The same considerations that rule out a cleft source for singular sluices rule out a cleft source for coordinated sluices. We show this by applying to coordinated sluices a subset of the ten diagnostics that Merchant (2001) used to argue against deriving singular sluices from clefts. Van Craenenbroeck (2010) showed some of Merchant’s original diagnostics to be inconclusive due to the fact that they do not distinguish between the cleft source and the non-elliptical wh-question source for the sluice.¹² Thus, we focus primarily on the diagnostics that do make this distinction.

The first diagnostic involves compatibility with adjuncts. Merchant shows that adjuncts can appear in sluices but not in clefts, as shown in (36a). The fact that adjuncts are possible in coordinated sluicing, as shown in (36b), shows that the coordinated sluice in (36b) cannot be derived from the coordinated clefts in (36c).

The second diagnostic concerns implicit arguments. Example (37a) shows that implicit arguments are possible as correlates of wh-phrases in sluicing constructions, but not as pivots of clefts. Implicit arguments are also possible as correlates of wh-phrases in coordinated sluices, as shown in (37b), which shows that coordinated sluices cannot be derived from coordinated clefts in (37c).¹³

The next diagnostic involves what Merchant refers to as ‘mention-some’ modification.¹⁴ He shows that wh-pivots in pseudoclefts are impossible with modifiers like ‘for example’. However, such modifiers can modify sluiced wh-phrases. This is shown in (38).

Coordinated sluices also allow ‘mention-some’ modification, as shown in (39):

The last diagnostic we consider involves case.¹⁵ Cleft pivots tend to have designated cases. For example, in languages in which wh-pivots in clefts are nominative, we expect to find wh-remnants in coordinated sluicing to be nominative as well if coordinated sluices are derived from coordinated clefts. We show with data from Polish that this is not what we find (see Sag and Nykiel 2011 for a discussion of case in Polish non-coordinated sluices).

Given the differences between coordinated sluicing and coordinated clefts discussed in this section, it is reasonable to conclude that the two constructions are not derivationally related.

In the next section, we present an analysis that derives the properties of coordinated sluicing and explains why these properties differ from the properties of constructions that we have entertained as possible sources of coordinated sluicing: coordinated wh-questions, multiple sluicing and coordinated clefts.

5 Analysis

The analysis of coordinated sluicing must account for the fact that coordinated sluicing is not subject to the clause-mate condition (unlike multiple sluicing), that there are no restrictions on the category of wh-phrases in coordinated sluicing (unlike in multiple sluicing), that coordination of arguments is possible in coordinated sluicing (unlike in CWHs), and that coordinated sluicing does not have the at-all reading (unlike CWHs).

Our starting point is the observation that in examples involving coordinated sluicing, such as the one in (41a), modeled after Merchant’s (1999: 484) examples, the interpretation of the second sluice is (41b), and not (41c): The speaker is not wondering whether Abby called some suspect, the speaker is wondering whether Abby called the suspect mentioned in the first conjunct (whoever he/she might be).

This interpretation is reminiscent of the interpretation, given in (42b), of single sluicing examples like (42a) below, discussed first by Merchant (1999).

Merchant proposes that in examples like (42a), the elided TP contains a pronominal correlate of the wh-trace in the antecedent clause, the ^Pe in (43). This pronominal correlate, according to Merchant, is interpreted as an E-type pronoun.

Building on this semantic similarity between examples of coordinated sluicing like the one in (41a) and examples involving coordinated questions with a single sluice, like the one in (42a), we propose that the two have the same underlying structure; i.e., that coordinated sluicing is derived from coordination of singular wh-questions, with an E-type pronoun in the second conjunct, co-indexed with the trace of the wh-phrase in the first conjunct (see also Scott 2012 and Barros and Kotek 2019), as shown in (44a–b).¹⁶

The bi-clausal structure we propose for coordinated sluices explains why coordinated sluicing does not have the properties found in multiple sluicing, coordinated wh-questions, or coordinated clefts. While coordinated sluices involve coordination of single wh-questions with ellipsis in each conjunct, multiple (non-coordinated) sluices, coordinated wh-questions, and coordinated clefts have different underlying structures, given (in a somewhat simplified manner) in (45a–c), respectively.

The structure we propose straightforwardly derives two properties of coordinated sluicing: the absence of the clause-mate condition and the absence of the restriction on the category of wh-phrases that can be coordinated.

The clause-mate condition – the requirement that multiple moving wh-phrases originate in the same clause – arises only when the multiple instances of wh-movement interact so that their paths either nest or cross. Abels and Dayal (2017a; b), for example, account for the clause-mate condition in multiple sluicing by assuming that covert wh-movement is clause-bound and subject to superiority (for these authors the second wh-phrase in a multiple sluicing configuration undergoes covert wh-movement). The fact that the restrictions that derive the clause-mate condition in multiple sluicing hold of covert movement implies that there is another, overt instance of wh-movement and the fact that one instance of wh-movement is overt and the other one is covert indicates that the two are, in some relevant sense, evaluated in the same domain, i.e., that they interact. On our analysis of coordinated sluicing, schematized in (46b), the two instances of wh-movement happen in separate clauses, unlike in multiple sluicing, schematized in (46a).

Since in (46b) there is no interaction between the two instances of wh-movement (neither is non-first in a single domain), it is expected that the clause-mate condition does not constrain coordinated sluicing, as shown by the grammaticality of the (b) examples and the contrast between the (a) and (b) examples in (47) and (48).

Our analysis also derives the fact that there are no restrictions on the category of wh-phrases that can be coordinated in multiple sluicing. Recall that English multiple sluicing is degraded if both wh-remnants are simplex wh-DPs and improves if the second wh-phrase is a PP (Bolinger 1978; Richards 1997; 2010; Lasnik 2014; Cortés Rodríguez 2019). This is shown by the contrast in (49).

Different authors account for this restriction in different ways. Lasnik (2007; 2014) attributes the ungrammaticality of (49a) to restrictions on extraposition. Recall that on his analysis, the first wh-remnant in a multiple sluicing construction undergoes leftward wh-movement to [Spec CP], while the second one undergoes extraposition, as shown in (50).

As shown in (51a–b), extraposition is sensitive to the DP vs. PP contrast in that PPs extrapose more easily than DPs do.

We have argued that coordinated sluicing is not derivationally related to multiple sluicing. Since on our analysis of coordinated sluicing, both wh-phrases undergo leftward wh-movement, there is no extraposition, and the absence of the preference for PPs is to be expected.

Richards (2010) accounts for the ban on multiple wh-DP remnants in multiple sluicing in a different way. As stated in Section 3.1, Richards assumes that multiple sluicing involves the structure in (52), where both wh-phrases undergo movement to [Spec CP].

(52)

Richards considers the ban on two wh-DP remnants in English sluicing to be a special case of a more general restriction on linearization that “rejects trees in which two nodes that are both of type α are to be linearized in the same Spell-Out domain” (Richards 2010: 5). He refers to this restriction, given in (53), as Distinctness.

In a multiple sluice, two wh-DP remnants cause the derivation to crash: fronting both wh-phrases to their left-peripheral positions creates the linearization statement <DP, DP>, which violates Distinctness.

Since on our analysis of coordinated sluicing the two wh-phrases are in separate clauses, they are never required to be linearized in the same Spell-Out domain. Thus, even when both wh-remnants are DPs, the illicit linearization statement is never created and Distinctness is obeyed.

The bi-clausal nature of our analysis does not in and of itself derive the availability of wh-argument coordination in coordinated sluicing, or the absence of the at-all reading. However, both of these properties follow from the presence of an E-type pronoun in the second conjunct (they), co-indexed with the trace of the wh-phrase in the first conjunct, as shown in (44b), repeated here as (54).

The presence of the pronoun in the second conjunct makes wh-argument coordination possible in coordinated sluicing by ensuring that the selectional properties of the verb are satisfied in both conjuncts; in the first conjunct, by the wh-phrase and the indefinite pronoun, and in the second conjunct, by the wh-phrase and the E-type pronoun (co-indexed with the trace of the wh-phrase in the first conjunct). Since the selectional properties of the verb are satisfied in both conjuncts, regardless of the type of wh-phrases or the type of the verb, coordination of wh-arguments is possible.

The presence of the pronoun in the second sluice also derives the absence of the at-all reading in coordinated sluicing. The at-all reading arises in coordination of wh-questions in which a wh-object that introduces one conjunct is not interpreted in the conjunct introduced by a wh-adjunct, as in the CWH in (55a). Since in coordinated sluicing the wh-object is interpreted in the second conjunct (via the E-type pronoun), the at-all reading is not available, as (56a–b) shows.

Finally, since coordinated sluicing involves coordination of two single questions, it captures the observation that coordinated sluices have only single pair readings and contrast in this respect with multiple (non-coordinated) sluices. This is shown by the contrast in (57), repeated from (29), where coordinated sluicing is unacceptable when the antecedent clause contains a distributive quantifier every and acceptable with the non-distributive some.

Our analysis makes the prediction, brought to our attention by Joe Emonds, that each of the two conjuncts should be able to undergo ellipsis independently of the other. We think this prediction is correct as long as no independent restrictions are violated. These independent restrictions include MaxElide, constraints against cataphoric dependencies, conditions on the interpretation of indefinites and/or the licensing of E-type pronouns. In the remainder of this section, we present examples that show that this prediction is borne out.

We start with examples in which ellipsis, instead of targeting TPs in the two conjuncts (as in (58a)), targets a TP in one conjunct and a VP in the other conjunct, as in (58b–c), or a VP in both conjuncts, as in (58d). All the examples with VP ellipsis are ungrammatical.¹⁷¹⁸

We attribute the ungrammaticality of (58b–d) to violations of MaxElide, which, in general terms, requires deletion of the largest possible constituent (see Fiengo and May 1994; Lasnik 2001; Takahashi and Fox 2005; Merchant 2008; Kimura 2013, among others).¹⁹ Our conclusion that (58b-d) are excluded because they violate MaxElide is corroborated by the contrast in (59a–b). The ungrammatical (59a) parallels (58b) in that the first of the coordinated sluices involves VP ellipsis, in violation of MaxElide. In the grammatical (59b), however, the sluice involving VP ellipsis contrasts with the antecedent clause, which results in the auxiliary being focused. The focused auxiliary is not part of the maximal string that can be deleted, so (59b) does not violate MaxElide even though, like the ungrammatical (59a), it involves VP ellipsis.²⁰

We turn next to examples in which ellipsis targets a TP only in one conjunct. The (a) examples in (60) and (61) are baseline coordinated sluicing examples, in which TP ellipsis takes place in both conjuncts. In the (b) examples, TP ellipsis takes place only in the second conjunct, and in the (c) examples only in the first conjunct. Crucially, both (b) and (c) examples are grammatical. For completeness’ sake, we also include (d) examples, in which there is no ellipsis in either conjunct.²¹

The examples in (60) and (61) show that the two instances of TP ellipsis in multiple sluicing are in principle independent, as one can take place without the other. However, things get more complicated in (62), which shows that not all logically possible TP deletions are grammatical. What distinguishes the examples in (62) from the ones in (60) and (61) above is the fact that the wh-pronoun what, which introduces the second sluiced conjunct, has an overt correlate something in the antecedent clause. The ungrammaticality of (62b) might be taken to indicate that in this case the second conjunct cannot be deleted. However, the fact that the non-elliptical (62d) is equally ungrammatical shows that the ungrammaticality of (62b) has nothing to do with ellipsis.

The problem with the examples in (62b) and (62d) appears to stem from the presence of two instances of the indefinite pronoun something: one in the antecedent TP Some students sang something, and the other one in the first conjunct which students sang something. Either instance of the indefinite something could in principle be the correlate of the wh-pronoun what in the second conjunct. However, the two indefinites necessarily introduce two different discourse referents (Heim 1982). Thus, what may be causing the degradation of (62b) and (62d) is the fact that both TPs (the TP Some students sang something and the first conjunct which students sang something) contain the correlate something, but the two correlates are non-identical since the referents of the two indefinites are different.

There is another question related to the grammatical coordinated sluicing example in (62a), where the TP in the first conjunct is deleted (together with the TP in the second conjunct). The question is whether the non-elliptical source of the first conjunct contains the indefinite something to being with. The interpretation of singular sluices such as the one in (63a) below suggests that it does not. The most natural interpretation of (63a) is not the one in (63b), in which the sluice contains the indefinite present in the antecedent TP, but the one in (63c), in which the sluice contains a pronoun coindexed with the indefinite in the antecedent.

Kim (2010) arrives at a similar conclusion based on the examples in (64) and (65a). She first notes that in (64) the two instances of someone refer to two different individuals, and discusses the source of the sluice in (65a) in light of this observation.

Kim states that if the source of the sluice in (65a) were (65b), we would also expect (65a) to be a statement about two different individuals, one committing a crime at a certain place and the other committing a crime at a certain time. This is not what (65a) means; it asks about the time and place of the crime committed by one and the same person. This leads Kim to propose (65c) as a source for (65a).

If this reasoning is on the right track, the source for the multiple sluice in (66a) does not contain an indefinite in the first conjunct (as in (62a), repeated as (66b)), but rather a pronominal element, as shown in (66c).

However, even when the indefinite is replaced with a pronoun that can be construed as an E-type pronoun, as in (66b), the sentence is degraded if this pronoun is pronounced. This is what examples (67a–b) show.

We attribute the ungrammaticality of these examples to a cataphora constraint, which in this case prevents the pronoun it from being coindexed with the wh-pronoun what following it (Kazenin 2002, for example). We take it to be the same constraint that excludes example (68a), which contrasts with (68b), where the pronoun stands in an anaphoric relationship with the preceding wh-phrase.

We thus conclude that in coordinated sluicing ellipsis may apply to each conjunct without applying to the other conjunct(s), as long as no independent constraints are violated.

6 Back to coordinated sluicing versus coordinated wh-questions

So far, we have shown that coordinated sluicing and CWHs have different properties, which we took as evidence that coordinated sluicing cannot be derived from CWHs. However, we have not addressed the question of why this should be the case: why do coordinated sluices differ from CWHs? In other words, what excludes the same source for both constructions?

If this were possible, the coordinated sluice in (69a) would be derived from the structure of CWH in (69b), and would presumably have the properties found in CWHs, which is not what we find (see the discussion of the differences between coordinated sluices and CWHs in Section 2.2).

(69)	a.	I know John sang, but I don’t remember what or where.
	b.	…but I don’t remember

We hypothesize that (69b) is excluded by economy. Our reasoning relies on an independently motivated assumption that operations apply only when they have an effect on pronunciation and/or interpretation (see Fox 2000).²² In the case at hand, the idea is that ellipsis can only apply if it has an effect on pronunciation. We adopt Merchant’s (2001: 60) proposal that ellipsis is triggered by an E(llipsis) feature, which instructs “the PF system to skip its complement for purposes of parsing and production.” In (69b), the E feature is located on C, and since both TP₁ and TP₂ are its complements, both have to be deleted. However, since deleting one TP (say TP₁) will already have deleted the string John sang, deleting TP₂ will have no further effect on pronunciation; such a vacuous application of ellipsis is banned by economy considerations.

In our analysis of coordinated sluicing, given in (70b), ellipsis also applies to two syntactic objects: TP₁ and TP₂, just as it does in (69b). However, each TP dominates a separate string, so both ellipsis operations have an effect on pronunciation. Thus, no ellipsis operation applies vacuously.

(70)	a.	I know John sang, but I don’t remember what or where.
	b.	…but I don’t remember

We next turn to a related question: why can’t CWHs be derived from the structure we posited for coordinated sluicing? What prevents the CWH in (71a) from having the structure in (71b) or (71c)?

We first consider (71b) as a possible source of the CWH in (71a). In this structure, the verb sing in the second conjunct does not contain a direct object; this forces an intransitive interpretation of the verb and yields the at-all reading of the CWH, as desired. However, if the string in (71a) were derived from (71b), it would mean that the sluicing remnant in the first conjunct – the wh-phrase what – has no overt correlate in the second conjunct, i.e., that its correlate is an implicit argument. Implicit arguments always take the lowest scope in their clause, as indicated, for example, by the fact that (72b) does not give rise to the same ambiguity as (72a) and that (73) is not ambiguous (Fodor and Fodor 1980). These examples show that an implicit argument (interpreted as an existential) does not interact with other quantifiers in the sentence; instead, it is always outscoped by them.

Given this, the structure in (71b) violates Scope parallelism (Romero 1998), which requires that the remnant of a deletion operation and its antecedent have the same scope. Scope parallelism is violated in (71b) because the wh-phrase what in the sluiced, first conjunct takes the highest scope in the clause, but its antecedent, the implicit argument in the second conjunct does not because it is outscoped by the fronted wh-phrase where. Thus, (71a) cannot be derived from (71b).

We next turn to (71c), repeated as (74), as a possible source for (71a). The structure in (74) contains a pronoun in the second conjunct that would presumably be pronounced,²³ yielding an incorrect string.

Our next question is what excludes (74). We believe that (74) is ungrammatical because the wh-trace in the first conjunct, which the E-type pronoun is coindexed with, is deleted. This may be related to the condition that requires the antecedent of an E-type pronoun to be overt and salient (Evans 1977; Kadmon 1987; Heim 1990; Chierchia 1992; Elbourne 2001; 2005; Patel-Grosz and Grosz 2010; Grosz et al. 2014, among others).²⁴ This is corroborated by the contrast in (75), where the (a) example (from Merchant 2001) contains no ellipsis in the first conjunct, and the pronunciation of the E-type pronoun in the second conjunct is licit. Our (b) example, in which the first conjunct is elided, no longer licenses the pronunciation of the E-type pronoun in the second conjunct.

However, the ungrammatical (75b) becomes grammatical if another possible antecedent for the pronounced E-type pronoun is added to the discourse, as shown in (76). Now, the preceding sentence contains the indefinite something, which serves as an alternative antecedent for the E-type pronoun it. Examples (77a–b) show that this holds more generally.²⁵²⁶

We conclude that the analysis in (71c) is impossible for CWHs because on such an analysis, the non-elided E-type pronoun in the second conjunct is always co-indexed with a copy of a wh-phrase that has undergone ellipsis. If this is illicit, we have an explanation for why CWHs cannot be derived in the same way as coordinated sluices.

7 Conclusion

We started with a puzzle concerning the ameliorating effect of coordination in multiple sluicing: why do the ungrammatical cases of multiple sluicing in English improve when the wh-phrases are coordinated?

We presented several arguments against the claim that coordinated sluicing is derived from coordinated wh-questions (CWHs). First, coordinated sluices allow wh-coordination to contain obligatory argument(s) of the verb, while CWHs do not. Moreover, coordinated sluices disallow at-all readings, while CWHs allow such readings. We also showed that coordinated sluicing cannot be derived from multiple sluicing: while multiple sluicing is, coordinated sluicing is not subject to the clause-mate condition. Also, unlike multiple sluicing, coordinated sluicing allows coordination of simplex DP wh-phrases. Finally, we showed, based on contrasts involving compatibility with wh-adjuncts, compatibility with implicit arguments, “mention-some” modification, and case considerations that coordinated sluicing is not derived from a coordinated cleft construction. Instead, we proposed a bi-clausal structure for coordinated sluices, which involves coordination of two CPs, with a single wh-phrase in the specifier of each CP and TP ellipsis in each CP. We justified the existence of this structure alongside the structure of CWHs by showing that the two constructions cannot share the same underlying source (either the one we posited for coordinated sluicing or the one of CWHs) because if they did, the derivation of one construction would involve a violation of a principle that is independently operative in the grammar.

Abbreviations

CWH = Coordinated Wh-Questions, DO = Direct Object, EPP = Extended Projection Principle, SP = Single Pair reading, PL = Pair-list reading, INSTR = instrumental, NOM = nominative, QL = Quantifier Lowering, QR = Quantifier Raising, PG = parasitic gap, RG = real gap, SSO = Scope Shifting Operations.

Competing Interests

The authors have no competing interests to declare.