3.1 Active vs. non-active voice

Hittite has a bivalent voice system with an opposition between active (ACT) and non-active (NACT) voice, the latter traditionally called “middle” or “mediopassive” (cf. Hoffner & Melchert 2008: 180). Voice is encoded on the verbal stem by a set of fusional inflectional suffixes, which also mark person (1ST, 2ND, 3RD), number (SG, PL), mood (IND, IMP), and — for indicative verb forms — tense (NPST, PST);¹ these suffixes are often referred to as inflectional “endings” because they always attach last to the verb and thus coincide with the right edge of the prosodic word.

The Hittite indicative active endings are given in Table 1 and the non-active endings in Table 2.² Note that while all Hittite verbs select the same set of non-active endings, verbal stems with active voice forms belong to one of two conjugational classes, the mi-conjugation (class I) or the ḫi-conjugation (class II), which are characterized by partially distinct inflectional endings. A verb’s class membership is a synchronically arbitrary lexical property. Class-specific endings are indicated as such in Table 1 with superscripts.

It can be observed in Table 2 that non-past tense non-active endings are optionally characterized by a particle –ri. Past tense non-active endings are distinguished from non-past by the presence of a final t, to which a particle –i may be optionally added.

The distribution of active and non-active voice morphology in Hittite is broadly similar to its distribution in other ancient IE languages, such as Ancient Greek, Vedic Sanskrit, Latin, and Tocharian, or in modern IE languages, such as Modern Greek or Albanian (cf. Grestenberger 2014a: 19–62, 102–5; 2018: 489–91).³ Active morphology is found in a wide range of syntactic contexts, whereas the distribution of non-active morphology is considerably more limited. Many verbs with active forms also surface with non-active morphology; for these verbs, the non-active marked verb forms are typically associated with a set of distinct functions, which include reflexives, reciprocals, anticausatives, and passives. These “oppositional” functions of Hittite non-active morphology vis-à-vis active morphology are illustrated in (1–4) below:⁴⁵

In addition, Hittite has a class of verbs that exhibit only non-active voice morphology in their basic stem forms. Members of this class — referred to here as media tantum (“middle only”) verbs — largely belong to semantic classes that tend to appear with non-active voice morphology in bivalent voice systems cross-linguistically (Kemmer 1993; Zombolou & Alexiadou 2014; Grestenberger 2018; 2019, i.a). Such canonical media tantum include the Hittite verbs in (5); the behavior of this class is illustrated in (6) with the stative verb ki– ‘lie’ and the change-of-state verb kiš– ‘become’.

The Hittite media tantum in (5) are not just semantically similar; they are also of a uniform syntactic type: all are syntactically unaccusative. This behavior is confirmed by independent diagnostics, which are discussed further in §3.2 below.

3.2 Unaccusativity in Hittite

Unaccusative verbs in Hittite show special morphosyntactic behavior by which they can be distinguished from transitive and even unergative verbs in certain syntactic contexts (cf. Hoffner & Melchert 2008: 280–3, 310 n. 7). The availability of such diagnostics of unaccusativity is an important feature that sets Hittite apart from the other ancient IE languages as well as from many non-IE languages, where the distinction among intransitive verbs between unaccusative and unergative is difficult to verify beyond lexical semantic classification. As will become clear in §4 below, this distinction plays a crucial role in the realization of Hittite voice morphology: (a subset of) unaccusative verbs show voice alternations between their basic stem form and their “imperfective” forms, whereas unergative verbs never show such alternations. This pattern can be observed precisely because the uniform syntax of these intransitive verbs can be reliably determined using independent criteria.

One diagnostic of unaccusativity is the distribution of enclitic pronouns. A unique feature of Anatolian languages like Hittite among the ancient IE languages is the existence of a set of 3rd person subject-marking enclitic pronouns (with gender-specific forms), which are given in (7):

(7)

The distribution of these enclitic subject pronouns serves as the most important diagnostic of unaccusativity in Hittite. Building on Watkins (1968–9: 93), Garrett (1990b; 1996) has demonstrated that only unaccusative verbs co-occur with these pronouns, which are required when a 3rd person subject is not overtly realized by a DP.⁶ In other contexts, subject pro-drop is obligatory; the enclitic subject pronouns in (7) thus never occur with agentive verbs, either transitive or intransitive (i.e., unergative), as illustrated in (8–9), where the subject is null:

In contrast, unaccusative verbs like the canonical media tantum in (5) above require the 3rd person enclitic subject pronouns in (7) when no DP subject is present; their presence is therefore obligatory in examples like (10):⁷

Hittite lacks 1st/2nd person enclitic subject pronouns, and so this diagnostic only applies with 3rd person arguments of unaccusatives verbs.

Unaccusative verbs also pattern differently from agentive verbs with respect to auxiliary selection in the formation of the periphrastic (or “analytic”) perfect construction.⁸ The periphrastic perfect in Hittite is functionally and formally similar to ‘have’-perfect constructions in Romance, Germanic, and elsewhere. In Hittite, the lexical verb is realized as a participial form and selects an inflected auxiliary verb, either ḫar(k)– ‘have’ or eš/aš– ‘be’. The choice of auxiliary verb is syntactically determined: as in (e.g.) Italian or Dutch, agentive verbs employ ḫar(k)– ‘have’, but unaccusative verbs instead use eš/aš– ‘be’.⁹ This morphosyntactic contrast is exemplified in (11) vs. (12–13) below:

Due in large part to the relative infrequency of the periphrastic perfect, most unaccusative verbs — including all of the media tantum discussed above — are not attested in this construction. However, in all attested cases the two diagnostics for unaccusativity pattern together: verbs that cooccur with subject clitics also select eš/aš– in the periphrastic perfect.

A further notable property of unaccusative media tantum is that they often have causative counterparts formed by adding the productive causative suffix –nu–, which derives a class I verbal stem.¹⁰ Verbs derived with this suffix are always transitive, and as expected receive active voice morphology in syntactically active contexts, e.g, (14):¹¹

Just like other transitive verbs formed with –nu–, causatives derived from media tantum are also compatible with non-active morphology, e.g., in passive or reflexive contexts (Luraghi 1992; Shatskov 2018; Inglese 2020: 171–2). For war-nu– in (14b) this usage is attested in (15):

3.3 activa tantum verbs in Hittite

While many unaccusative verbs in Hittite are media tantum, it also has a substantial class of diagnostically unaccusative verbs that surface with only active voice morphology in their basic stem forms. We refer to this class as activa tantum (cf. Grestenberger 2018: 501 for the term).

Hittite activa tantum belong broadly to the same semantic classes as unaccusative media tantum: compare (16) below with (5) above. Note that, in addition to a number of synchronically non-derived verb stems, the activa tantum include the productive class of deadjectival inchoative verbs — traditionally referred to as “fientives” — formed with the suffix –ešš– (Hoffner & Melchert 2008: 177–8; cf. Watkins 1971; Hoffner 1998).¹²,¹³

Syntactically, Hittite activa tantum behave just like canonical media tantum: they obligatorily co-occur with enclitic subject pronouns in the absence of an overt DP subject, as in (17). Once again, this behavior contrasts with that of transitive and unergative verbs like (12–13) above.

Similarly, activa tantum contrast with transitive and unergative verbs with respect to their choice of auxiliary in the periphastic perfect, selecting eš/aš– ‘be’ rather than ḫar(k)– ‘have’, as in (18) below:

A third way in which unaccusative activa tantum behave like media tantum is that many of them also form causatives with the suffix –nu–. Such causatives are attested for numerous activa tantum, e.g., (19); these include non-derived verbal stems like (19a–d), as well deadjectival verbs derived with the suffix –ešš– like (19e).¹⁴

As evident in (19), causatives derived from activa tantum take active morphology in syntactically active contexts. However, they can also be passivized with non-active morphology; this pattern is attested for ašnu– ‘take care of’ in (19a), e.g., in (20):

Thus insofar as Hittite activa tantum pattern with unaccusative media tantum like (5) with respect to the morphosyntactic diagnostics discussed above, they appear to be prototypical unaccusative verbs not just semantically but also syntactically. That is, there is no reason to believe that activa tantum and media tantum differ syntactically. (We will postpone until §5 explicit discussion of what that structure might be.) Morphologically, however, the activa tantum contrast with unaccusative media tantum, the former surfacing only with active morphology in their basic stems forms and the latter only with non-active morphology. As pointed out by Grestenberger (2018: 501), “[f]ormally active unaccusative verbs” of this kind are “a major problem for understanding the canonical distribution of voice morphology” in languages with bivalent voice systems: if it is the case that the class of unaccusative verbs which have identical syntactic characteristics and thus presumably have an identical structural representation are realized with non-active morphology (a widely adopted idea since Embick 1998), then the active morphology seen in Hittite activa tantum would, descriptively, “mismatch” its syntactic context (cf. Weisser 2014).

One solution to this problem, proposed by Alexiadou & Anagnostopoulou (2004), Schäfer (2008), and Alexiadou et al. (2006; 2015) and adopted by Grestenberger (2018), is that the activa tantum differ syntactically from unaccusative media tantum in a way that is not reflected in the unaccusativity diagnostics discussed previously — specifically, that the former lack the Voice layer present in the latter, which is responsible for the realization of non-active morphology. For these authors, the term “mismatch” applied to activa tantum is a misnomer, because in fact the morphology does reflect the syntax. The details of this proposal are discussed further in §6, where we argue explicitly against this kind of analysis; instead, we contend that Hittite supports the view that unaccusative activa tantum are “mismatch” verbs in much the same way as Hittite deponents, which we discuss now in §3.4.¹⁵

3.4 Deponent verbs in Hittite

Although most media tantum in Hittite are syntactically unaccusative (like (5) above), Hittite also has a small class of transitive verbs that surface with only non-active morphology in their basic stem forms. Following Grestenberger (2014a; b; 2018; 2019), we refer to verbs with these properties as DEPONENT verbs. Deponents constitute a closed morphological class in Hittite; a complete list of securely attested deponent verbs is provided in (21):¹⁶

While deponent verbs differ morphologically from active-marked transitive verbs, syntactically they behave in the same way: deponents take direct objects marked with ACC case and never co-occur with enclitic subject pronouns. The examples in (22a–b) illustrate accusative object marking, while (22c) with null subject further demonstrates that deponents do not occur with subject pronouns.

In addition, there is some evidence (albeit limited) to suggest that deponents select ‘have’ in the periphrastic perfect construction just like active-marked transitive verbs; this pattern can be observed in (23):¹⁷

However, one respect in which deponent verbs differ from active-marked transitive verbs is that they appear to lack corresponding finite passive forms.¹⁸ Grestenberger (2018: 496–7) suggests that this fact should be understood as a morphological blocking effect: passivization is unavailable for deponents because the non-active morphology regularly used to form passives of transitive verbs (see §3.1 above) is already employed in their syntactically active forms.¹⁹

Thus, the only clear difference between deponents and active-marked transitive verbs is in their morphology: deponents exhibit non-active inflection, which in this syntactic context is anomalous within Hittite and cross-linguistically.

3.5 “Aspect” in Hittite

The preceding sections identified two classes of Hittite verbs which exhibit a mismatch between syntax and morphology: activa tantum, which are syntactically unaccusative but take active inflectional endings (3.3); and deponents, which are syntactically transitive but take non-active inflectional endings (3.4). These two mismatch classes are bolded in Table 3, which summarizes the relationship between syntax and voice morphology in the Hittite verbal classes discussed above.

In §4 below, we will show that the two mismatch verbal classes in Table 3 also interact in an idiosyncratic way with what are traditionally referred to as “imperfective” suffixes (Hoffner & Melchert 2008: 318). This section provides a concise description of the formal and functional properties of these suffixes. The labels “imperfective” and “imperfective stem” are used descriptively to refer to these suffixes and verbal stems containing them; we return to the issue of their exact grammatical function at the conclusion of the section.

Hittite has four verb-forming suffixes that attach to a root or verbal stem and determine its conjugational class (I or II).²⁰ One is the productive causative suffix –nu– (class I), which was discussed already in §3.2 and §3.3 above. The other three are the imperfective suffixes –ške– (class I), –anna/i– (II), and –šša– (II) (Hoffner & Melchert 2008: 322–3). The latter two suffixes have a restricted distribution: just a few verbs use –šša– to form their imperfective stems, while –anna/i– is associated especially (although not exclusively) with the deponent verbs listed in (21) above.²¹ The suffix –ške–, in contrast, is highly productive: it is regularly employed by the vast majority of Hittite verbs to form their imperfective stems and in this function spreads diachronically at the expense of the other two suffixes.²² The usage of these deverbal suffixes is illustrated in (24–26):

Imperfective verbal stems of the type in (24–26) are associated with a range of aspectual meanings, including continuative, habitual, distributive, frequentative, and iterative.²³ These readings are exemplified in (27–31):²⁴

Two additional facts about Hittite imperfectives can be observed in these examples. The first is that any of the meanings in (27–31) can also be expressed by a verb’s basic stem (i.e., without an imperfective suffix).²⁵ Thus, for instance, in (30) both penneškanzi (‘they drive’) in the main clause and turiyanzi (‘they hitch up’) in the preceding adjoined relative clause function as frequentatives, but only the former contains an imperfective suffix.²⁶ Further support for this view comes from cases in which a verb’s imperfective stem stands in correspondence with its basic stem in different copies of the same Hittite text, e.g., tūriezzi (‘he harnesses’; KBo 6.2 iii 60): tūriškezzi (‘id.’; KBo 6.3 iii 65) (cf. Inglese & Mattiola 2020); this apparent interchangeability suggests that these forms could be perceived by Hittite scribes as functionally equivalent.

The second is that all three Hittite imperfective suffixes are grammatically equivalent (“suppletive allomorphs of a single morpheme” per Melchert 1998: 414). Their functional identity is supported, in particular, by examples like those in (31), where iterativity is expressed by a –ške-marked verbal stem in (31a) and by –šša- and –anna/i-marked stems in (31b). Their equivalence is confirmed, moreover, by the “supine construction” (Hoffner & Melchert 2008: 322, 338), a type of periphrastic ingressive/inchoative construction meaning roughly ‘begin to X’ in which a finite form of the verb d(a)i– ‘place’ or tiye/a– ‘step; take one’s place’ combines with a verbal noun in its lexical value (i.e., X is the lexical meaning of the verbal noun). This construction requires that the verbal noun be formed from a marked imperfective stem (by adding a nominalizer suffix –wan (SUP)); as evident in (32), any one of the three imperfective suffixes satisfies this requirement:

The range of meanings available to verbal stems marked with these suffixes have led some scholars to analyze them as markers of imperfective aspect (Cambi & Bertinetto 2006; Cambi 2007). Alternatively, Inglese & Mattiola (2020) argue (building on Dressler 1968) that the suffix –ške– in particular is a pluractional marker, which could naturally extend to the other imperfective suffixes. Which of these analyses is correct will have implications for the morphosyntax of Hittite imperfectives. Whereas an imperfective marker would be expected to head the functional projection associated with grammatical aspect (“viewpoint aspect” in the sense of Tenny 1987; Smith 1991), van Geenhoven (2004; 2005) analyzes pluractional markers as modifiers of lexical (or “situation”) aspect, which occupy a lower structural position (cf. Laca 2002; 2004a; b; 2006; MacDonald 2008; Travis 2010).

We take no strong stance on this issue here. Under the proposal that we develop in section §6 below, the crucial fact about these suffixes is not their hierarchical structure but their morphological linear position, intervening between the verbal root and voice morphology. For the present, then, we retain the labels “imperfective” for these suffixes and “Aspect” for their functional projection, and leave it to future research to determine the precise syntactic status of these suffixes and, in turn, how they come to stand in this position.

Finally, a reviewer asks whether the aspectual suffixes could not be realizations of the verbalizing head v. This is unlikely. The verbalizer v has distinct morphological realizations (the causative –nu– and the inchoative –ešš–, discussed in §3.3). As these are not in complementary distribution with any of the aspectual suffixes, we conclude that they are not in competition to realize the same head.

4.1 Non-interactions between aspect and voice

We begin with the general case. Transitive verbs whose basic stem forms show active morphology in syntactically active contexts have imperfective stems that also show active marking in these contexts. This generalization is exemplified with the verb p(a)i– ‘give’ in (33), where the basic stem and imperfective stem occur in effectively identical contexts and both receive active endings:

Similarly, the imperfective stems of the transitive verbs in (34–36b) show the same active marking as their corresponding basic stems in (34–36a). Note, too, that these imperfective stems are also compatible with non-active marking, in which case they exhibit the same set of functions as their basic stems do in non-active contexts — e.g., passive in (34c) and (35c), reflexive in (36c):²⁸

Unergative verbs behave similarly when an imperfective suffix is present. Unergative verbs that receive active morphology in their basic stem forms show the same marking in their imperfective stems. This pattern is illustrated in (37–38) with the verbs palwai– ‘make noise’ and link– ‘swear’. The unergative syntax of these verbs in their basic stem forms was established already in (9a) and (9b) above; the absence of subject clitics with their imperfective stems in (37–38) is likewise indicative of unergativity.

The situation with imperfective stems of unaccusative media tantum verbs is less certain due to the poverty of evidence for this type.²⁹ What little evidence is available, however, suggests that these verbs show the same non-active marking in their imperfective stems as in their basic stem forms, as can be seen in (39) with the –ške-suffixed imperfective of the media tantum eš/aš– ‘sit down’. A second likely example is (40), where the imperfective suffix –ške– attaches to a reduplicated form of the media tantum verb ištu– ‘become evident’; the resulting stem išdušduške– exhibits non-active marking just like its base ištu–. Dempsey (2015) has shown that verbal reduplication in Hittite is associated with fundamentally the same set of aspectual functions as the imperfective suffixes, and these two marking strategies often co-occur as in (40) (with semantically “reinforcing” effect per Dempsey). We assume that the diagnostic value of this form is not compromised by the presence of reduplication, which on its own does not otherwise appear to have any effect on voice morphology: for instance, the transitive verb par(a)i–([pr(a)i–]) ‘blow’ has a reduplicated stem paripr(a)i–([pri-pr(a)i–]), both of which take active endings in syntactically active contexts (e.g., 3PL.NPST.ACT priyanzi (KUB 2.3 ii 30): parippariyanzi (KBo 15.49 iv 9)), and similarly — a more direct parallel for ištu– — the unaccusative media tantum verb kiš– ‘happen; become’ has a reduplicated stem kikkiš– that likewise shows non-active marking (e.g., 3SG.NPST.NACT kišari (KUB 1.13 i 13): kikkištāri (KUB 14.5 rev. 10)).³⁰ In addition, the alternating verb nai/ne– ‘turn’, which in the intransitive sense ‘turn oneself’ exhibits only non-active inflection, also shows non-active inflection in imperfective forms with this meaning, as in (41).

The examples in (34–41) uniformly support the view that imperfective stems exhibit the same voice morphology as do their bases in equivalent syntactic contexts. This distribution suggests that voice is fundamentally independent of aspect in Hittite, the latter having no effect on its realization. To reiterate: aspectual morphology appears consistently with both active and non-active morphology, and the morphological realization of voice is contingent on and predictable from the syntactic context.

Before proceeding to the two verbal classes that problematize this generalization, however, it is necessary to briefly discuss the chronology of the preceding examples. In §4.2 below, we demonstrate that in Old and Middle Hittite imperfectives of unaccusative activa tantum show voice reversal vis-à-vis their basic stem forms. It is therefore crucial that (37–38) and (39–40) are attested in Middle Hittite: these examples provide evidence for a synchronic contrast in the older language (i.e., prior to New Hittite) between unaccusative activa tantum and other intransitive verbs — on the one hand, active-inflecting unergative verbs, and on the other, non-active inflecting unaccusative media tantum — whereby only the unaccusative activa tantum exhibit voice reversal.³¹ Similarly, §4.3 below shows that imperfectives of deponents show voice reversal in Old Hittite; it is important, then, that (33) also occurs in Old Hittite, since it shows that ordinary transitive verbs with active-inflecting basic stems do not show voice reversal in their imperfective stem during this period.

4.2 Interactions between aspect and voice in activa tantum

In contrast to the deponents examined in §4.3 below, the distribution of voice morphology in Hittite activa tantum has been previously studied. Concerning this class, the first important observation was made by Watkins (1969: 72), who pointed out that the very frequent unaccusative verbs pai– ‘go’ and uwa– ‘come’ take only active endings in their basic verbal stem, but almost exclusively non-active endings in their –ške-suffixed imperfectives. Neu (1968a: 86–9) noted the same behavior in the verb ak(k)– ‘die’ and the productive class of deadjectival change-of-state verbs formed with the suffix –ešš– (discussed in §3.3 above).

This pattern of voice reversal has now been systematically treated by Melchert (2017), who established two crucial facts. The first is that it is restricted to unaccusative activa tantum. Unergative intransitive verbs with active inflection like palwai– ‘shout’ and link– ‘swear’ thus exhibit the same active inflection in their imperfective forms as in their basic stem forms, as discussed already in §4.1 above.³² The other is that all unaccusative activa tantum consistently show voice reversal in their imperfective forms in Old Hittite.³³ Melchert’s (2017) survey of the evidence reveals that exceptions to this pattern — i.e., diagnostically unaccusative verbs with active-inflected imperfective forms — are limited to New Hittite texts and copies of older texts produced during the New Hittite period. Table 4 lists imperfective forms of activa tantum attested in manuscripts produced during the Old and Middle Hittite periods.³⁴³⁵

Yet while voice reversal is exceptionless only in the older language, there are also a number of imperfectives of activa tantum that are first attested in New Hittite texts or copies of older texts and show the same voice reversal. Examples of this type are provided in Table 5.³⁶ In New Hittite, however, these imperfectives which exhibit voice reversal coexist with imperfectives that show the same active inflection as their base, e.g.: IPFV.3PL.NPST.ACT paiškanzi ‘they go’ (VBoT 74:5); IPFV.3SG.NPST.ACT akkiškezzi ‘he dies’ (KUB 9.31 iv 45), IPFV.3PL.PST.ACT gallareške[r] ‘they turned out unfavorably’ (KUB 5.22:35). Given such variation, it is difficult to determine the grammatical status of voice reversal for activa tantum in New Hittite; however, the exceptionlessness of this pattern in the older language argues that voice reversal was obligatory for this type at least in Old Hittite (and probably beyond into Middle Hittite).

4.3 Interactions between aspect and voice in deponents

Like the activa tantum just discussed in §4.2, deponents exceptionally exhibit an interaction between aspect and voice: imperfectives of deponents select active endings in the same syntactic contexts as their base stems select non-active endings. While the evidence for deponents is much less robust (see further discussion below), voice reversal in this class is similarly exceptionless in Old Hittite; imperfectives of deponents attested in original manuscripts of Old Hittite texts are given in Table 6.³⁷

This voice reversal pattern in Hittite deponents has not, to our knowledge, been previously noticed. This is in all likelihood due primarily to the seriously limited nature of the usable evidence, which is restricted by (i) the fact that deponents are rarer by type and token than unaccusative activa tantum and (ii) the well-established diachronic tendency for deponents to adopt active inflection in their basic stem forms,³⁸ thus eliminating the mismatch between syntax and voice morphology that is characteristic of this class (cf. §3.4 above).

This tendency can be observed already in Middle Hittite,³⁹ including for all of the deponents that also have imperfective forms attested at this historical stage; thus while these imperfective forms almost consistently show active inflection just like the Old Hittite forms in Table 6, it is not clear that they are examples of voice reversal in the same sense, since they stand beside basic stem forms with active inflection, and are thus consistent with the principle established in §4.1 above that imperfectives in general exhibit the same voice morphology as their basic stem forms in equivalent syntactic contexts. Examples of such contemporaneous attestation in Middle Hittite include: IPFV.3PL.NPST.ACT paršiannianzi (KUB 24.98:11) beside 1SG.PST.ACT paršiyanun (KBo 23.27 ii 39) to parš(i)– ‘break’; 3SG.IPFV.PST.ACT šarraškit (KUB 23.72 obv. 37) beside 3SG.PST.ACT šarraš (KUB 23.72 rev. 3) to šarra– ‘transgress’; and IPFV.3PL.IMP.ACT [t]uḫšanniyandu (KUB 35.146 iii 11′) beside tuḫḫušzi (KBo 20.39 l.col. 16’) to tuḫš– ‘cut off’. In the case of iškalla– ‘pierce’, the imperfective is attested in Middle Hittite with active inflection (3SG.IPFV.NPST.ACT iškalliškizzi; KBo 3.21 i 6), whereas active-inflected forms of the basic stem occur first in New Hittite (e.g., 3SG.NPST.ACT iškallai; KBo 6.4 i 39), but their absence during the earlier period may be due simply to accident of attestation.

The imperfectives of deponents that are first attested in New Hittite are for the same reasons non-probative, their active inflection being contemporaneous with or subsequent to the appearance of active inflection in their basic stem forms — e.g., IPFV.3PL.NPST.ACT ararkiškanzi (KUB 11.25 iii 19–24) beside 3SG.NPST.ACT ārki (KBo 10.45 iv 32) to ark– ‘mount’;⁴⁰ IPFV.3SG.IMP.ACT paḫḫaškeddu beside 2PL.IMP.ACT paḫḫašten (KUB 23.82 rev. 5, 12) to paḫš– ‘protect’; IPFV.2SG.NPST.ACT wešieškeši (KUB 24.7 ii 57) beside 3SG.IMP.ACT w<e>šeddu (KUB 30.24 ii 4) to wešiye/a– ‘graze’.

In addition, a few apparent counter-examples to voice reversal begin to appear in the post-Old Hittite period. The imperfective of the verb šarra– ‘transgress’ shows non-active inflection in its 3SG.NPST form in five independent occurrences (e.g., šarrašketta; KUB 36.75 + Bo 4696 i 8), as well as once in its 2PL.NPST form (šarriškettuma; KUB 34.75:5).⁴¹ There is also a single example of an imperfective to ark– ‘mount’ with non-active inflection, IPFV.3SG.NPST.NACT arkišketta (KUB 29.1 i 30). How these non-active forms should be explained is unclear, especially since they occur beside contemporaneous imperfective forms of the same verbs with active inflection, e.g., šarraš in Middle Hittite and ararkiškanzi in New Hittite (both cited above).

The evidence for voice reversal in deponents is thus somewhat less robust than for the unaccusative activa tantum treated in §4.2 above, but the overall picture is broadly similar. The few examples of deponents attested in Old Hittite all show voice reversal.⁴² The later evidence mostly accords with Old Hittite, but its diagnostic value is compromised by the emergence of active inflection in the basic stem forms of historically deponent verbs during this period.

4.4 Exceptional interactions between aspect and voice

It was established in §4.2 that in Old and Middle Hittite unaccusative activa tantum consistently show voice reversal, their imperfective forms exhibiting non-active morphology in the same syntactic contexts as their basic stem forms unexpectedly show active morphology. §4.3 then demonstrated that in Old Hittite deponents show the converse voice reversal pattern, their imperfective forms exhibiting active morphology where their basic stems unexpectedly show non-active morphology. In Old Hittite, at least, there is thus a contrast between these two verbal classes and all other morphosyntactic types which, as shown in §4.1, do not undergo voice reversal. Table 7 provides a summary of the distribution of voice morphology in Old Hittite by morphosyntactic type.

Thus far a satisfactory synchronic explanation of voice reversal has proved elusive even for the better studied activa tantum; for a critique of earlier proposals see Melchert (2017: 478–9). Beyond their failure to take into account the chronological distribution of forms, the central problem that faces these accounts (especially Neu 1968a: 89) is, per Inglese (2020: 184), “the lack of synchronic functional motivation of the pattern in Hittite.” This issue is starkly illustrated for the activa tantum by (42–43), where the active-inflected basic stem forms of pai– ‘go’ and park-ešš– ‘become tall’ occur in the same passages as their corresponding (bolded) non-active-inflected imperfective forms. For deponent verbs the same is evident in (44), where the non-active inflected basic stem form of parš(i)– ‘break’ similarly cooccurs with its (bolded) active-inflected imperfective:

Examples like (42–44) are striking because there is no obvious contrast between the imperfective and basic stem forms of these verbs modulo the aspectual meaning associated with the imperfective suffix. From a functional perspective, then, the voice reversal observed in these forms appears to be essentially arbitrary. Recognizing this issue, Melchert (2017: 482–4) tentatively suggests a diachronic explanation for the activa tantum, suggesting that the voice alternations seen in Hittite activa tantum — i.e., basic stem forms with active inflection vs. derived –ske-forms with non-active inflection — was inherited from PIE. The evidence cited for this hypothesis, which comes exclusively from Tocharian, is both limited and mixed, and thus in our view insufficient to justify reconstructing the pattern.⁴³ Yet however Melchert’s hypothesis is ultimately assessed, what is perhaps most relevant for the present analysis is that the Tocharian evidence does not support the possibility (suggested by a reviewer) that the Hittite suffix –ške– was at a diachronically earlier stage idiosyncratically associated with non-active morphology (i.e., +DEP in terms of the analysis developed in §6 below). There is therefore no historical basis for assuming that Hittite –ške– has any such association, which would not in any case explain why the suffix triggers “voice reversal” only in Hittite activa tantum. Moreover, even if Melchert’s hypothesis were correct for the unaccusative activa tantum, the converse voice reversal pattern in deponents would still require a separate explanation.

In the next two sections, we propose a unified account of voice reversal in Hittite. Under our analysis, the fact that only activa tantum and deponents show voice reversal in their imperfective forms is related directly to another unique property of these verbal classes — namely, that their basic stem forms exhibit voice morphology that mismatches their syntactic context. The rationale underlying our proposal is that these mismatches are “fixed” when additional verbal morphology intervenes between the basic verb stem and inflectional endings. In other words, what appears to be “voice reversal” in imperfectives vis-à-vis their basic stem is just the emergence of syntactically expected voice morphology. However, before presenting our own analysis in §6, we first discuss previous accounts of the morphosyntax of Voice in §5.