2.1 Clause structure basics

Samoan (Samoic Outlier, Polynesian, Austronesian) is head-initial, and displays a predominantly VSO word order;² a T(ense) – A(spect) – M(ood) marker appears clause-initially; (5).

Collins (2016) builds a compelling argument – on the basis of coordination, negation, and complex predicate patterns – that verb-initial word order is derived from movement of the VP⁴ to a functional projection below TP (labelled FP in (6); its precise identity is undetermined).⁵ Crucially, a DP object moves out of the VP – to spec vP – prior to (remnant) VP fronting (I will later posit that this is for interpretative reasons, following Aldridge 2004). Following Massam (2001a) and Longenbaugh and Polinsky (2017) for Niuean, and Collins (2013; 2016) for Samoan, I assume that movement of an internal DP targets the lower vP specifier; the external argument is merged in a higher, outer vP specifier, akin to “Tucking in” proposed by Richards (1997; 2002).⁶ This structure is shown in (6) (the specifics of v/Voice will be revised in forthcoming sections, however).

(6)	Samoan clause structure

2.2 Ergative and absolutive case

Samoan has an ergative-absolutive alignment: transitive subjects are marked with the prenominal ergative marker e (7a), while transitive direct objects (7a), and intransitive subjects (7b, c), appear (mostly) with no case marker (glossed as ABS).

Ergative is commonly analysed as an inherent case (e.g., Woolford 1997; Legate 2002; 2008; Aldridge 2004; see Collins 2013 for the Samoan ergative), assigned to an external argument by v⁰, hand-in-hand with an external (e.g., agent) theta role.

(8)	Inherent Ergative case

Applying the inherent ergative analysis to Samoan, however, requires some modifications. As Koopman (2012) points out, the Samoan ergative is not restricted to subjects that are traditionally regarded as semantic “agents”: inanimate DPs (e.g., natural forces, items of machinery) may appear with ergative case, as do experiencers of certain psych-predicates (e.g., lagona ‘feel’, iloa ‘know’; I discuss this in further detail in §5.3). Note that such criteria may not necessarily be viewed as grounds for rejecting the inherent ergative approach entirely: the theta-role tied to ergative case, and assigned by v⁰ to the externally-merged DP, may not necessarily be exclusively associated with a narrow set of semantic criteria such as animacy (see also Legate 2012, for related discussion). In view of this, and in anticipation of the present analysis, I adopt a modified version of the inherent hypothesis, treating ergative as being assigned by v⁰ to its external argument under a SPECIFIER-HEAD Agree relationship (see also Assmann 2015). I refer to this as “Spec-Head ergative”, although it does not differ greatly from the inherent approach, other than that it is not necessarily tied to an “agent” theta-role, in the traditional narrow sense. Theta roles are discussed in greater detail in section 4.

As for absolutive case, Legate (2002; 2008) and Aldridge (2004) identify two types of absolutive systems. In the first type, absolutive case is assigned structurally by (finite) T⁰ to the closest case-less DP (much like nominative case): either to an intransitive subject, or a transitive object (recall that the transitive subject has already received ergative case from v⁰, leaving the object as the closest case-less DP). In the second type, absolutive is a morphologically unmarked default for two separate abstract cases: nominative, assigned by T⁰ to intransitive subjects, and accusative, assigned by v⁰ to transitive objects. Although Samoan absolutive is less marked than ergative, Yu (2015) argues that it does not have null phonological spell-out: it is realized by a high tone on the last mora of the word preceding the absolutive.⁷ Furthermore, Mosel and Hovdhaugen (1992: 143) and Yu and Özyildiz (2016) note that absolutive DPs (most commonly, proper names) are optionally marked by prenominal ia (9).

Since Samoan absolutive is therefore not morphologically unmarked, Koopman (2012) proposes as a null hypothesis that absolutive is assigned by a single source, namely T⁰, and is therefore analogous to nominative case. Conversely, Collins (2013) proposes that Samoan absolutive is a morphological default for abstract nominative and accusative case, and falls under the second category. Because nothing crucial in the analysis presented in this paper hinges upon the choice between these two alternatives, I will for the sake of concreteness assume the single source approach (i.e., absolutive = nominative, following Koopman 2012); see footnote 23 however for discussion of how Collins’ (2013) analysis may also be accommodated under my proposal.

2.3 Unergatives (and their objects)

Subjects of unergative verbs in Samoan are always absolutive; ergative case never marks an unergative subject (10). Following the Spec-Head ergative approach prima facie, this suggests that they are not merged in the specifier of vP (or at least, not an ergative case-assigning vP).

Deal (2010) proposes a version of ergative case assignment in which object agreement (with v⁰) is a necessary condition for ergative case assignment to a subject. This type of approach could potentially capture the Samoan data in (10): the absence of an object of dance means that ergative case assignment necessarily fails. The picture becomes more complex, however, when unergative verbs are transitivized: the addition of an object does not restore ergative case marking on the subject. As shown in (11) though (13), unergatives do not exhibit an ERG-ABS case configuration even when an object is added; instead, the subject appears as absolutive, and the object is marked with prenominal i.

An ERG-ABS case array is indeed ungrammatical; (14).

There are two exceptions to this pattern. As for the English unergative verb sing, Samoan has two different verbs, usu and pese. Usu obligatorily follows an ERG-ABS pattern, but cannot be used without an object, as in (15). Milner’s (1966) Samoan dictionary translates usu into English as ‘sing (a song)’ (Milner 1966: 304). Usu is therefore obligatorily transitive (and may not be a direct translation of English sing).

Unlike usu, pese exhibits the same unergative-transitive alternation as English sing. When an object is present, as in (16b), the ABS-i frame is obligatory – just as in (11)–(14).

Besides usu, I can find only one exception to the ABS-i case patterning of unergatives: the unergative verb tatalo (‘pray’) obligatorily follows an ERG-ABS pattern when an object (e.g., talosaga ‘prayer’) is added.

A consultant reported that ABS-i patterning would have the meaning of ‘pray to (someone)’. It is therefore possible that an ERG-ABS pattern arises as in order to avoid ambiguity between the frames [pray + DP] and [pray to + DP]. Because it is likely that pray is more frequently used with the latter frame than with the former, the ABS-i case marking in (17b) is blocked, as a means of differentiating [pray + DP] from the more expected [pray to + DP] (i is used as a prepositional marker in Samoan, as I will discuss in depth shortly). It may also be that the English translation of (17b) is not an entirely accurate rendition of the original Samoan.

The exceptions of usu (‘sing’) and tatalo (‘pray’) aside, Samoan UNERGATIVE + OBJECT constructions overwhelmingly follow a non-ergative case pattern. This suggests that the presence of an object is not the sole syntactic difference between unergative and transitive predicates in Samoan: when transitivized by the addition of an object, unergative verbs do not conform to the same (ergative-absolutive) case frame observed in transitive sentences such as (5). What underlies this difference? In the next section, I investigate the ABS-i case pattern further, by turning to another set of predicates in which it appears: the Samoan “middle”.

3.1 Quantifier float

The first piece of evidence to suggest that middle objects are direct, as opposed to indirect objects is based upon the behaviour of the quantifier ‘uma (‘all’). Seiter (1978) shows that ‘uma can be moved from its modifying DP (23a) and attached as a post-verbal clitic; (23b, c, d). This applies unrestrictedly to any non-pronominal subject (23b, c) or direct object (23d).

Like subjects and direct objects, oblique DPs can also be modified by floating ‘uma.

According to Seiter (1978), however, oblique quantifier float is subject to two restrictions which do not apply to direct objects (or subjects). Oblique quantifiers may undergo float only if they are both (i) animate and (ii) the first DP after the verb (hence the grammaticality of 24), but not otherwise, as shown in (25).

Significantly, these restrictions do not hold of middle objects, which may launch quantifiers regardless of animacy or position of the DP with respect to the verb, as in (26).

As Seiter notes, this supports a syntactic treatment of middle objects as direct objects. A full analysis of the restrictions on oblique ‘uma float is beyond the scope of the present paper; the relevant point here, is that i-marked objects of middle verbs pattern as direct objects, as opposed to oblique DPs.

3.2 Clitic placement

Samoan has a set of pronominal subject clitics, which are morphologically distinct from full pronouns (a full paradigm is given in Mosel & Hovdhaugen 1992: 122, 374). While subjects are typically post-verbal (27a), subject clitics must appear in a preverbal position, without case marking; (27b).

Third singular pronominal subjects may cliticize only in transitive clauses (28a); cliticization of a third singular subject in an intransitive clause is ungrammatical¹⁰ – even with a prepositional DP present; (28b).

Unlike intransitive subjects, however, third singular middle subjects may cliticize (29), which suggests that middle verbs are formally transitive.

First and second person (1/2) pronouns are widely argued to contain a richer featural composition than third person (3rd) pronouns. For example, Harley and Ritter (2002) – among many others – argue that 1/2 pronouns encompass a [+participant] feature which 3rd pronouns lack. Adopting this approach, the data in (28–29) suggest that Samoan subject cliticization is sensitive to [+participant] (and/or indeed any other feature common to 1/2 pronouns but not present in 3rd pronouns), unless a direct object is present. While an analysis of the sensitivity of cliticization to transitivity is a topic for future research, the crucial observation to be made here is that middle objects allow for 3rd subject pronoun clitics (29b), in contrast to oblique objects (28b), which does not. The Samoan middle, therefore, displays the hallmarks of a transitive predicate, as opposed to an intransitive predicate with an oblique object.

3.3 Pseudo-Noun Incorporation

Samoan displays VOS order with bare NP objects, which are interpreted semantically as indefinite, non-individuated, and non-affected (30, 31). The subject bears absolutive case.

Massam (2001b) observes this same phenomenon in the related Polynesian language Niuean, proposing that the type of VOS in (30b, 31b) is derived from lack of NP movement out of the VP prior to VP raising (to FP; see §2.1). Because the object does not move out of the VP, it raises along with the verb, thus appearing directly adjacent to it. Massam refers to this as “Pseudo Noun Incorporation” (PNI); note that that the object does not morphologically incorporate (hence “pseudo”).

Samoan PNI applies to all direct objects (bar a few lexical exceptions), but not to oblique locatives,¹¹ as in (32b), or to ditransitive goal arguments (33b) – even though the direct object in ditransitive constructions may incorporate (33c).

Objects of middle verbs, however, are able to undergo PNI.¹²

The behaviour of middle objects is therefore akin to that of absolutive direct objects, and unlike ditransitive goal objects or locative objects – suggesting that middle i-case is not oblique.

3.4 Unergatives again

Before discussing the identity of middle i-case, I return to the UNERGATIVE + OBJECT construction (recall that this displays the same ABS-i case pattern as middles). Applying the above tests for transitivity and direct objecthood to the UNERGATIVE + OBJECT construction, we find that it indeed behaves in the same manner as the middle construction: the quantifier ‘uma may be floated despite inanimacy of the object (35b), third singular subjects may cliticize (35c), and objects may undergo PNI (35d).

Like middles, UNERGATIVE + OBJECT constructions exhibit the syntactic hallmarks of a transitive construction, consisting of a subject and direct object – and much like an ERG-ABS transitive. This is unsurprising in view of the standard syntactic treatment of unergatives as discussed in section 1, namely that transitive and unergative constructions are alike in consisting of a VP-external subject, but differ only in the presence vs. absence of an internal object. The question to be addressed is why Samoan unergatives – and middles – do not display a typical transitive ERG-ABS case array. I approach this from two perspectives: first, how middle/unergative and ERG-ABS verbs differ semantically (§4) and second, the resulting structural differences which give rise to the two case frames (§5).

5.1 What is i-case?

Having established that middle and unergative i-marked objects are not prepositional objects, an important clue as to the identity of the i-marker lies in its role elsewhere in the Polynesian family. While i indeed functions as an oblique or prepositional marker in Samoan (and more widely throughout Polynesian), it also serves as a structural ACCUSATIVE case marker in those related Polynesian languages with accusative alignment; e.g., Maori (44a), and Hawaiian (44b). Note from (44b) in particular that Hawaiian i case serves both as an accusative marker (marking the direct object) and oblique marker (marking the indirect object). Indeed, Chung (1978: 49–50) remarks that “the case marking of canonical transitive clauses in accusative languages resembles that of middle clauses in all Polynesian languages”.

A treatment of Samoan i-case as structural accusative is consistent with its appearance on raised (i.e., non-thematic) arguments. Certain middle predicates such as mana’o (‘want’) and fia maga’o (‘hope’) take clausal complements, and allow the embedded subject to raise from its base position (45b, 46b), to a clause-peripheral position, where it is marked with i.¹⁷

While sentences such as those in (45) and (46) are often referred to as “raising-to-object” constructions in Polynesian literature, Massam (1985) argues for related Niuean that the relevant movement does not, in fact, target the object position of the matrix clause.¹⁸ Rather, the raised DP remains in the embedded CP, occupying a CP-peripheral specifier position, labelled as “SPEC2” in (47). Here, it is assigned structural case, from a relevant case-assigning head in the matrix clause, via ECM.

(47)	Raising-to-object in Polynesian (Massam 1985)

Bejar and Massam (1999) propose a theory of Multiple Case Checking in order to account for several cross-linguistic constructions (including Polynesian raising-to-object) in which a DP appears to receive more than once case. Their claim is that, in Multiple Case constructions, the case of a DP is interpretable only if the DP remains in the appropriate checking configuration with its case-assigning head: once the DP moves, case must be reassigned. Applying this to the Samoan raising in (45b) and (46b), the raised DP (le teine in (45) and Sarah in (46)) first receives case in the lower clause. After raising into the specifier of CP, however, the DP is no longer in its original case-checking configuration, and case must therefore be re-checked. Since both (45) and (46) contain middle matrix verbs (mana’o in (45) and fia maga’o in (46)), i-case is available to be assigned to the raised DP.

For the present purposes, the relevant point is that Samoan i-case may be assigned to derived objects, which are not thematically selected by the middle verb; this suggests that a treatment of i-case as structural case (as opposed to lexical or inherent case) is most appropriate. I therefore propose that i-case used to mark the Samoan unergative and middle object is structural accusative case (glossed henceforth as ACC); Samoan hereby has two transitive case frames: ergative-absolutive, and absolutive-accusative. This type of analysis is not without precedent: Aldridge (2011) argues that Malagasy (Austronesian) also has two transitive frames, which reflect its intermediate stage on a continuum of re-analysis from a fully ergative – to a fully accusative – aligned language.¹⁹ I turn now to the question of how case is assigned in Samoan, and what governs the split in transitive case patterns.

5.2 Case assignment in Samoan

I begin this section with a brief recap of Samoan case markers: in section 2.2, I addressed the nature of ergative and absolutive case. I treat absolutive as a structural case, assigned by T⁰ to the closest DP with unvalued case, just as is nominative case (see Koopman 2012). Ergative case, conversely, is assigned in a specifier – head configuration (“Spec-Head ergative”); I will propose in this section that the relevant head here is Voice⁰. Middle/unergative i-case was identified in section 5.1 as structural accusative, and is assigned by v⁰, as will be discussed shortly. A summary is given in Table 1.

5.2.2 Two case frames

As for the second, more familiar Samoan transitive case frame – ergative-absolutive – two questions arise: first, how does it differ structurally from the absolutive-accusative frame? And second, why does it differ? What is the function of a second transitive case pattern? Here, I expand on a proposal by Massam (2009; to appear) for the related language Niuean (see also Polinsky 2016; Tollan 2016). Massam claims that unergative subjects are structurally lower than ergatives. Treating both unergative and middle subjects as PROTO-LOW AGENTS, to the exclusion of ergative subjects (PROTO-HIGH AGENTS), I propose that proto-low agents are introduced (and assigned their proto-role) by v⁰. Ergative subjects – proto-high agents – are introduced by a higher thematic head, namely Voice⁰. The additional phrasal structure of ERG-ABS constructions corresponds to the additional properties encompassed by ergative proto-high agents in (39a) which distinguish them from proto-low agents in (39b), namely iii through vii (either all of these properties, or a subset of them). Recall that properties i and ii characterize both high and low agents. As such, i and ii are contributed by v⁰, while iii through vii are contributed by Voice⁰. This is illustrated in (50) and in Table 2.

Table 2

External argument and predicate types.

	Predicate types	Proto-role	Introduced by
Low external	ABS-ACC Middle, unergative	Low agent	v0
High external	ERG-ABS transitive	High agent	Voice0

(50)	External argument positions in Samoan

The partition of vP and VoiceP is well-established in the literature: a split v/Voice structure has been adopted by Alexiadou et al. (2006), Pylkkännen (2008), Coon (2013), Harley (2013), and Legate (2014), besides many others. Both Massam (2009; to appear) and the present analysis differ, however, by arguing that both split heads are responsible for introducing (different types of) external arguments. I further demonstrate how the difference between arguments introduced by v⁰ and those introduced by Voice⁰ may result in split case patterning.

5.3 Voice morphology

Some support for the claim that Samoan ERG-ABS (high) transitives involve more structure than ABS-ACC (low) transitives comes from a small number of middle verbs, including fesili (‘ask’; 52a), and vala’au (‘call’; 53a). These verbs may also pattern as ERG-ABS (52b, 53b), but require the addition of the suffix –C(i)a (in which the initial consonant and high vowel are determined based on phonotactics) to do so.

Under the analysis in section 5.2, –C(i)a can be treated as a spell-out of Voice⁰. This provides some evidence that ERG-ABS predicates involve more structure than ABS-ACC predicates (as opposed to being derived from a different flavor of vP with a different featural composition, in the sense of Folli and Harley 2004, and Aldridge 2012). It should be noted, however, that this type of derivation is not fully productive, applying only to a minority of middle verbs.²⁵ Furthermore, two experiencer verbs in particular – iloa (‘know’) and lagona (‘feel’) – which might be expected to pattern as low transitive, appear obligatorily with an ERG-ABS case array. As pointed out by Koopman (2012), however, both of these predicates are “morphologically complex”: both comprise the –C(i)a Voice suffix (see also Milner 1966 for further discussion). It is also worth noting that –C(i)a functions as a passive suffix in nominative-accusative Polynesian languages (e.g., Maori), which is further indication of its status within the family as a Voice marker.

I turn now to the distribution of the causative prefix fa’a, which provides further indication that ERG-ABS transitives involve additional structure. Fa’a can be added to an unaccusative verb to form a causative counterpart, with ERG-ABS case patterning, as in (54).

It can also be added to unergative verbs, with the meaning of “make X do something”; (55). The causer is marked ergative and the causee absolutive.

When added to middle (ABS-ACC patterning) verbs, the causer is ergative, the causee absolutive, and object accusative; no other case pattern is acceptable (56).²⁶

Notice that fa’a causatives formed from middle and unergative verbs demonstrate a key prediction of the structure proposed in (50), namely that both VP-external argument positions can be occupied simultaneously: (55b) and (56b) both exhibit an ergative causer (taken to occupy spec, VoiceP) and an absolutive causee (taken to occupy spec, vP). Furthermore, the presence of an accusative object in (56b) demonstrates that ergative- and accusative-marked arguments indeed do co-occur. Here, the high-agent causer (le tama ‘the boy’) receives Spec-Head ergative case from Voice⁰, while the low-agent causee (le teine ‘the girl’) and object (le masi ‘the cookie’) are both assigned structural case: the causee receives absolutive case from T⁰, and the object receives accusative case from v (which is able to assign accusative, by having introduced the external causee). The structure of (56b) is shown below.²⁷

Comrie (1975) characterizes causative marking as increasing the valency of a predicate by one argument. In the examples above, I suggest that fa’a spells out Voice⁰, and introduces an externally-merged high agent. If ERG-ABS pattering predicates already bundle VoiceP, then one crucial prediction is that they should be unable to be causativized by fa’a, because there should be no place in the structure for it (assuming, following Grohmann 2003, that VoiceP constitutes the edge of the thematic domain). This prediction is indeed borne out: ERG-ABS verbs cannot be causativized by fa’a (58, 59).²⁸

The intended meanings in (58b, 69b) must be expressed instead with a biclausal construction, which is translated loosely as ‘X compelled Y to do Z’.

This supports an analysis in which ERG-ABS transitives involve more phrasal (here: thematic) structure than ABS-ACC transitives.²⁹

5.4 Pseudo-Noun Incorporation and unergatives

As discussed earlier, Samoan exhibits VOS word order with bare objects, as in (61b). This is known as Pseudo-Noun Incorporation (Massam 2001b). The subject of a PNI construction is absolutive; the object appears with no determiner or case marking,³⁰ and is interpreted as indefinite and non-specific (Chung 1978). According to Massam’s analysis, PNI objects are NPs (or at least, do not contain D structure), and therefore do not require case-licensing. They fail to raise out of VP prior to VP fronting, thereby appearing adjacent to the verb, as illustrated below. The VOS word order of PNI hereby results from the absence of object movement.

While there is no consensus on the motivation for object movement, I follow Aldridge (2004)’s proposal for Tagalog, in which she claims that DP objects must raise in order to obtain a referential interpretation. Raising out of VP – to vP – allows for the object to escape existential closure, which would ensue if it were to remain VP-internal (Diesing 1992). In the context of the current paper, an important observation to be noted is that PNI (i.e., non-referential) objects never appear with proto-high agents (i.e., ergative-marked subjects).³¹ This raises questions regarding the precise nature of the relationship between the properties of an agent subject, and the properties of a theme object. In this section, I discuss how this may be dealt with within the current approach; first, why the subject of a PNI predicate is always an (absolutive) proto-low agent as opposed to a proto-high agent, and second, how the relationship between agent and theme is instantiated in the syntax.

5.4.2 Object raising

To recap from earlier discussion: when a theme object is referential, it is realised as a full DP, and must raise out of the VP. In this case, the subject may be either a proto-low or proto-high agent, depending on a number of parameters. Conversely, pseudo-incorporated objects are semantically non-referential, and non-specific. PNI objects are realized as NPs (i.e., lacking DP structure), and do not raise out of VP (Massam 2001b). Subjects of PNI constructions are always mapped as proto-low agents (merged in vP) bearing absolutive case. Here I discuss the structural instantiation of this.

In the thematic domain, the merge of VoiceP – the thematic projection which introduces a proto-high agent, bearing ergative case – appears to be contingent upon the syntax of the lower argument. Object movement – to the specifier of vP – is required if VoiceP is to be merged. Conversely, object movement does not require the merge of Voice⁰: the object in low transitive (middle and UNERGATIVE + OBJECT) constructions is assumed to have raised out of VP (cf. 49), yet a non-ergative case frame arises, indicating that the agent is mapped to the proto-low role.

To account for this, I draw upon a proposal by Hale and Keyser (2002), aimed at explaining causative-inchoative alternations in terms of asymmetries in lexical structure. Specifically, Hale and Keyser note that certain verbs, such as sink (62a) can undergo transitivity alternations, while others, such as sparkle (62b), cannot.

(62)	a.	The boat sank.
		The storm sank the boat.
	b.	The diamond sparkled.
		*The sun sparkled the diamond.

Hale and Keyser propose that the asymmetry between (a) and (b) is due to a difference in the structure forming possibilities of the lexical roots sink and sparkle. Verbs such as sink and sparkle minimally consist of a verbal host and a lexical root (which later incorporates with the host via a process known as “conflation”). The difference between sink and sparkle lies in whether the root requires the projection of a specifier: sink does (63a), whereas sparkle does not (63b).

Crucially, only if the verbal projection contains a specifier can further verbal structure be merged (labelled here as V₂; this is potentially a causative light v head). As such, the V₁ maximal projection in (b) must combine directly with its single DP argument (e.g., the diamond) – no further verbal structure building is possible due to the absence of a specifier in the lower projection (in other words, because the already-present verbal structure is not maximally saturated).

(63)

a.

b.

Expanding this principle from the lexical domain to the VP-external event domain,³² we can explain from a structure building perspective why the high agent-introducing thematic head – namely VoiceP – is not merged in PNI constructions: vP contains no specifier. The unattested derivation is one in which VoiceP is merged, but the specifier of vP is empty, as in (64).

(64)	Unattested derivation
	[VoiceP DP Voice0 [vP v0 [VP V0 (NP)]]]

Only if the specifier of vP is filled – either by a raised internal argument (as in any high transitive) or by a merged low external argument (e.g., as in a causativized unergative such as (55b)) – can Voice⁰ be merged. This is characterized below in (65).

(65)	VoiceP may be merged if vP contains a specifier, filled either by a moved internal argument and/or by a merged (low) external argument.

Note, however, that (65) is not a bi-conditional: the presence of a specifier in vP is a prerequisite for the merge of Voice⁰, but not a sufficient factor. VoiceP is not present in low transitives, despite movement of the internal argument (i.e., an unergative or middle object) to spec vP.³³ Essentially, Voice⁰ is only merged if the relevant predicate also requires a proto-high agent. The merge of an agent in VoiceP, is hereby ultimately determined by the properties of the agent, but is concurrently dependent on the properties of the lower argument.

5.5 Summary

The various clause types and patterns of case assignment are summarized Table 3.

In the final discussion section, I consider the cross-linguistic implications of split v/Voice system I have proposed for Samoan.

6.1 Cross-linguistic variation

The main claim of this paper is that Samoan exhibits two external argument positions, which results in two transitive case frames. Crucially, unergative subjects are merged lower than ergative subjects (see also Massam 2009; to appear): the lack of an object in unergatives is not the only factor which distinguishes them from ERG-ABS transitive frames. In this final section before concluding, I address some of the wider theoretical issues and typological predictions raised by this proposal. What is the potential range of cross-linguistic variation? Are unergative subjects merged lower than transitive subjects in all languages?

First, it should be stressed that Samoan unergative subjects are merged in the same position as some types of transitive subjects, namely the subjects of “middle” predicates. Under this approach, unergatives and some transitive subjects share common properties, while high agent ergative subjects are thematically “peripheral” (in the sense of Kim 2011). There is no a priori reason to maintain that every language should exhibit the same split v/Voice system proposed for Samoan – or, if so, for the two proto-roles to be governed by the same sematic criteria. In contrast to Samoan, for example, Niuean does not allow inanimate ergative agents (Massam 2006), suggesting that inanimate agents cannot be mapped to the proto-high role in Niuean.

Looking beyond Polynesian, different variants of the ergative alignment pattern are observed. In a number of so-called “active” languages (e.g., 66, 67), unergative subjects are marked with ergative case (see Bittner & Hale 1996; Woolford 2015) – exactly as predicted by the standard approach to argument structure shown in (1) coupled with an inherent (or Spec-Head) theory of ergative case. Unaccusative subjects and direct objects surface as absolutive.

This suggests that active languages do not make the same syntactic distinction between high and low agents that is evident in Samoan: all external arguments are merged in a single v/VoiceP, and assigned ergative case by v/Voice⁰. It is also expected that an alignment may undergo historical change and/or dialect variation arising from splitting or collapsing of vP and VoiceP. This is precisely what we find in Basque: while western dialects (67) exhibit an active alignment, with unergative and transitive subject both marked ergative, eastern dialects exhibit the same type of alignment as Samoan, with unergative an unaccusative subjects both surfacing as absolutive. Since eastern dialects are reported to be more conservative, and western dialects more innovative (Aldai 2008), this change conceivably amounts to a collapsing of vP and VoiceP in the western dialects, while the split v/Voice system persists in eastern dialects. Another possibility for active languages would involve the v/Voice split of the type recently proposed by Harley (2013) and Legate (2014), in which v does not introduce an argument, such that all proto-agents are merged in VoiceP.

6.2 On the absence of dedicated unergative morphology

One final typological puzzle remains. The split v/Voice structure proposed in this paper might predict the existence of languages in which unergative subjects are marked differently from both transitive subjects and internal arguments (unaccusative subjects and direct objects). So far, nothing in the theory presented here explicitly rules out a language with a split vP structure in which v⁰ and Voice⁰ both assign a uniquely marked Spec-Head case, as in (68).

(68)	Hypothetical Bi-ergative language

To my knowledge, no such language has ever been reported. Why should such a typological gap arise, if the grammar allows the option to merge transitive and unergative subjects in different positions?

The reason for the absence of (68) may lie partially beyond the realm of the narrow syntax. Du Bois (1987; 2017) argues extensively that ergative systems are isomorphic to inherent patterns of human discourse, proposing a “Preferred Argument Structure”, in which transitive subjects are more likely to be avoided more than any other core argument (i.e., intransitive subject; transitive object) in discourse. Ergative alignments are, according to Du Bois, a grammatical manifestation of universal discourse preferences: as a (partial) result of being least favoured in sentence production, transitive subjects are most morphologically marked. Intransitive subjects are much more widespread than transitive subjects; Du Bois relatedly observes in a corpus study that intransitive clauses are more prevalent than transitive clauses. Given these preferences, it is unsurprising that intransitive subjects are most commonly unmarked cross-linguistically. Since unergative verbs are (for the most part) intransitive, there would be no usage-based motivation for a language to develop a grammar which would license them in a unique way, especially if they could be licensed by another means (e.g., by T⁰).

Considering also the properties of proto-low agents as compared with proto-high agents, high agents have several distinctive featural properties which low agents lack (i.e., a-iii through a-vii in (39)). By contrast with high agents and patients, there is nothing inherently distinctive at all about low agents: of the four properties in (39) which characterize low agents, two – initiation and experience of an event (b-i and b-ii) – are shared with high agents. The other two features (b-iii and b-iv) can be characterized as defaults to denote the lack of properties typical of either high agents (i.e., causing a change in state or affecting another entity) or patients (i.e., undergoing a change in state or being affected by the event). Thus, the absence of languages with a morphological “Case B” follows from the relative semantic unmarkedness of proto-low agents compared with other arguments, which would likely constrain any potential motivation of a grammar to mark them in a distinctive manner.