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3.3.3.Infinitival clauses
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Like finite relative clauses, infinitival clauses may provide information about an antecedent. Some examples are given in (511), in which the first infinitival clause is interpreted as restrictive and the second as non-restrictive: in (511a) the infinitival clause restricts the denotation of the modified noun phrase, whereas in (511b) it provides additional information about the antecedent. Note that some speakers prefer an appositive reading for (511b), for which reason we added the question mark; cf. Section 3.1.3.

511
Restrictive and non-restrictive infinitival clauses
a. Dit is een machine [om hout mee te schuren].
  this  is a machine  comp  wood  with  to sand
  'This is a machine to sand wood with.'
b. ? Zoʼn machine, [om hout mee te schuren], is vrij goedkoop.
  such a machine  comp  wood  with  to sand  is fairly cheap
  'Such a machine, to sand wood with, is fairly cheap.'

In this modifying function, infinitival clauses are always introduced by the infinitival complementizer om, and, as usual with om-infinitives, the infinitival verb is obligatorily accompanied by the infinitival marker te. The infinitival clauses contain two interpretative gaps. The first gap is the implied subject PRO, which we find in all infinitival om + te-infinitives and which receives an arbitrary interpretation in the examples under discussion. The second interpretative gap in (511) is the complement of the instrumental PP headed by mee'with'; it is generally assumed that this complement is some empty category that is coindexed with the modified noun phrase een/zoʼn machine, and which we will from now on refer to as empty operator (abbreviated as OP in the examples). It is reasonable to assume that this empty operator has moved out of the PP into clause-initial position by means of R-extraction since the preposition surfaces in its stranded form mee, not in its non-stranded form met. This all amounts to saying that the representations of the examples in (511) are as indicated in (512), in which IC stands for infinitival clause and the coreference and antecedent-trace relations are indicated by superscripts.

512
a. Dit is een machinei [IC OPi om PROarb hout [PP mee ti] te schuren].
b. Zoʼn machinei, [IC OPi om PROarb hout [PP mee ti] te schuren], is vrij goedkoop.

It seems natural to assume that the empty operator is a covert relative pronoun and that the infinitival clauses in (511) are in fact relative clauses, but we will see later in this section that there are problems with this assumption. The examples in (513) furthermore show that the distinction between restrictive and non-restrictive clauses is not exhaustive, and that we have to distinguish two types of restrictive infinitival clause.

513
Two types of restrictive infinitival clause
a. Dit is een machine [om hout mee te schuren].
type I
  this  is a machine  comp  wood  with  to sand
  'This is a machine to sand wood with.'
b. We zoeken een meisje [om op onze baby te passen].
type II
  we  search  a girl  comp  after our baby  to look
  'Weʼre looking for a girl to look after our baby.'

The two examples differ in the number of interpretative gaps they contain. We have already seen above that (513a) has the representation in (512a), repeated below as (514a), and contains two interpretative gaps, the implied subject PRO and an empty operator that is coreferential with the antecedent of the clause. Example (513b), on the other hand, does not contain an empty operator, and it is the implied subject PRO that is interpreted as coreferential with the antecedent of the infinitival clause; since there is no evidence that movement is involved in this construction, we will assign (513b) the representation in (514b). Infinitival clauses of the form in (514b) cannot be used non-restrictively.

514
a. Dit is een machine [IC OPi om PROarb hout [PP mee ti] te schuren].
type I
b. We zoeken een meisje [IC om PROi op onze baby te passen].
type II

The three types of infinitival clause will be discussed more extensively in separate subsections. Subsection IV concludes with a brief discussion of two constructions that can be easily confused with the infinitival clauses discussed above.

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[+]  I.  Restrictive infinitival clauses containing an empty operator

This subsection discusses restrictive infinitival clauses containing an empty operator in more detail. We start with the question as to whether these infinitival clauses can be considered relative clauses. After that we address whether there are any restrictions on the antecedent of the empty operator or the infinitival verb.

[+]  A.  Are restrictive infinitival clauses with an empty operator relative clauses?

The fact that infinitival clauses of the type in (512/514a) arguably contain an empty operator that is moved into clause-initial position suggests that we are dealing with regular relative clauses, where the relative pronoun simply has no phonetic realization. There are, however, several problems for this suggestion. The first is only circumstantial, and is concerned with the fact that German actually cannot readily use infinitival clauses in this modifying function (Kester 1994: 3.3.4.4), which is clear from the fact that a Dutch example such as (515a) cannot be directly translated into German, as shown by the unacceptability of (515b). Given the fact that Dutch and German are so closely related, it would be very surprising if the first could make use of infinitival relative clauses, but the latter could not.

515
a. Ik zoek een boeki [OPi om PRO morgen ti te lezen].
  search  a book  comp  tomorrow  to read
  'Iʼm looking for a book to read tomorrow.'
b. * Ich suche ein Buch [um morgen zu lesen].

      The second problem is a more serious one. As can be seen in (516a'&b'), infinitival clauses containing an empty operator can also occur in predicative position, an option that, as is shown in (517), does not exist for regular finite clauses. This suggests that the infinitival clause is comparable to the set-denoting adjectives in that it can be used both predicatively and attributively.

516
a. Dit is een boeki [OPi om PRO in één adem uit te lezen].
  this  is a book  comp  in one breath  prt.  to read
  'This is a book to read out in the same breath.'
a'. Dit boeki is [OPi om PRO in één adem uit te lezen].
  this book  is  comp  in one breath  prt.  to read
b. Dit is een boeki [OPi om ti te zoenen].
  this  is  a book  comp  to kiss
  'This is an absolutely delightful book.'
b'. Dit boeki is [OPi om PRO ti te zoenen].
  this book  is  comp  to kiss
  'This book is absolutely delightful.'
517
a. Dit is de jongeni [diei gisteren ti ziek was].
  this is the boy  who  yesterday  ill  was
  'This is the boy that was ill yesterday.'
b. * Deze jongeni is [diei gisteren ti ziek was].
  this boy  is who  yesterday  ill  was

      A third problem is that infinitival clauses are often used in the presence of adjectives that may enter the so-called easy-to-please construction in the primed examples in (518), the analysis of which also involves an empty operator; see Section A6.5, sub IVA for more discussion. Given the semantic similarities between the primeless and primed examples, it seems reasonable that the former are the attributive counterparts of the predicative constructions in the latter.

518
a. Dat is een gemakkelijk boeki [OPi om PRO ti te lezen].
  that  is  an  easy book  comp  to read
  'That is an easy book to read.'
a'. Dat boeki is gemakkelijk [OPi om PRO ti te lezen].
  that book  is  easy  comp  to read
  'That book is easy to read.'
b. Dat is een leuke jongeni [OPi om PRO ti te ontmoeten].
  that  is a nice boy  comp  to meet
b'. Die jongeni is leuk [OPi om PRO ti te ontmoeten].
  that boy  is  nice  comp  to meet

At this point German comes in again. It can be noted that German does not have easy-to-please construction of the type in (518a'&b'): *Das Buch ist einfach um zu lesen. German does have constructions such as Das Buch ist einfach zu lesen without the infinitival complementizer um, but these must clearly be analyzed as modal infinitives, which is also clear from the fact that the infinitive can be used in pronominal attributive position das (leicht) zu lesende Buch, where it is realized in the form of an attributively inflected present participle; cf. the discussion in Subsection IVB. It therefore seems plausible to relate the ungrammaticality of (515b) to this fact; infinitival clauses are actually more like infinitival clauses in the easy-to-please construction than like regular relative clauses.
      Leaving the precise analysis of the restrictive infinitival clauses in this subsection for future research, we may safely conclude from the discussion above that infinitival clauses containing an empty operator are either set-denoting phrases that can be used either predicatively or attributively, or belong to the adjectival part of an easy-to-please construction that can be used in these functions. Despite appearances, there is no clear evidence that infinitival clauses are relative clauses.

[+]  B.  Restrictions on the antecedent of the empty operator

Given the conclusion that the infinitival clauses under discussion are not relative clauses, and that the empty operator is therefore not a relative pronoun, it does not come as a surprise that there are no restrictions on the antecedent in terms of number, gender or animacy. This is illustrated in Table 6.

Table 6: The antecedent of the empty operator
singular plural
non-neuter animate een man om op te bouwen
a man comp on to build
‘a man to rely on’
mannen om op te bouwen
men comp on to build
‘men to rely on’
inanimate een dag om nooit te vergeten
a day comp never to forget
‘a day never to be forgotten’
dagen om nooit te vergeten
days comp never to forget
‘days never to be forgotten’
neuter animate een meisje om op te bouwen
a girl comp on to build
‘a girl to rely on’
meisjes om op te bouwen
girls comp on to build
‘girls to rely on’
inanimate een boek om direct te lezen
a book comp at once to read
‘a book to read at once’
boeken om direct te lezen
books comp at once to read
‘a book to read at once’

There do not seem to be any further restrictions either: the antecedent can be definite, indefinite, or quantified. Thus, while in Table 6 all antecedents are indefinite, the antecedent in (519a) is a definite DP and in (519b&c) the antecedent is quantified.

519
a. Jan is de mani [OPi om PRO het [PP aan ti] te vragen].
  Jan is  the man  comp  it  to  to ask
  'Jan is the man to ask it to.'
b. Jan is geen mani [OPi om PRO [PP op ti] te bouwen].
  Jan  is  no man  comp  on  to build
  'Jan isnʼt a man you can rely on.'
c. Ik heb alle boekeni [OPi om PRO ti te lezen] in mijn kamer gelegd.
  I have  all books  comp  to read  in my room  put
  'I have put all books to read in my room.'

For completeness’ sake, it can be noted that noun phrases modified by a restrictive infinitival clause often have a nominal compound as their counterpart in which the verb of the infinitival clause is used as the first morpheme. The relation between the two morphemes of these compounds is typically one of purpose. Some examples are given in (520).

520
a. een zaal om in te lezen
  a room to read in
a'. een leeszaal
  a reading room
b. een machine om mee te schuren
  a machine to sand with
b'. een schuurmachine
  a sanding machine
c. een hond om mee te waken
  a dog to watch with
c'. een waakhond
  a watchdog
[+]  C.  Restrictions on the infinitive and the empty operator

There seem to be some restrictions on the types of verbs that can appear in the modifying infinitival clause, and the syntactic function of the empty operator. For obvious reasons, infinitival clauses with an empty operator normally do not occur if the infinitival verb is intransitive or unaccusative, as in (521a&b); of course, both examples are acceptable, but must be analyzed without an empty operator: in these examples it is the implied subject PRO that is interpreted as the element coreferential with the antecedent. It should be noted, though, that this restriction is not absolute; example (524) will show that there are means to circumvent this restriction.

521
Intransitive verb
a. Hij is geen jongeni [om PROi hard te werken].
  he  is no boy  comp  hard  to work
  'He isnʼt the kind of boy that works hard.'
b. Dit is geen artikeli [om PROi in een taalkundig tijdschrift te verschijnen].
  this  is no article  comp  in a linguistic journal  to appear
  'This is no article to appear in a linguistic journal.'

An infinitival clause gives rise to a perfect result if the infinitive is a transitive verb, as in (522a): in this case the empty operator corresponds to the direct object. If the verb is ditransitive, the result depends on the form of the indirect object; constructions with a nominal indirect object are much less acceptable than constructions with a prepositional indirect object. The (b)-examples show that for constructions in which the empty operator acts as the direct object, and the (c)-examples for cases in which it corresponds to the indirect object.

522
Transitive and ditransitive verbs
a. Dit is een boekenkasti [OPi om PRO zelf ti in elkaar te zetten].
  this  is a bookcase  comp  oneself  together  to put
  'This is a bookcase one has to put together oneself.'
b. ?? Dit is geldi [OPi om PRO de kerk ti te schenken].
  this  is  money  comp  the church  to donate
  'This is money meant to be donated to the church.'
b'. Dit is geldi [OPi om PRO ti aan de kerk te schenken].
  this  is  money  comp  to the church  to donate
  'This is money meant to be donated to the church.'
c. *? Dit is een goed projecti [OPi om PRO ti geld te geven].
  this  is a good project  comp  money  to give
c'. Dit is een goed projecti [OPi om PRO geld [PP aan ti] te geven].
  this  is a good project  comp  money  to  to give
  'This is a good project to give money to.'

Given the fact that the empty operator can act as the complement of the preposition aan in (522c'), it will not come as a surprise that the result is also fine if the empty operator acts as the complement of a PP-complement of the verb as in (523a). Example (523b) shows that the empty operator may act as the complement of a locational predicate.

523
Verbs with a PP-complement or locational predicate
a. Dit is een onderwerpi [OPi om PRO goed [PP over ti] na te denken].
  this  is  a topic  comp  well  about  prt.  to think
  'This is a topic to reflect on well.'
b. Dit is geen caféi [OPi om PRO gezellig [PP in ti] te zitten].
  this  is  not a bar  comp  cozily  in  to sit
  'This isnʼt a bar to sit in cozily.'

Finally, the empty operator may correspond to the complement of a PP-adjunct, provided at least that this PP allows R-extraction. Examples of this sort were already given in (520), and some more examples are given in (524). Note that if such adjuncts are present, the construction can also appear with intransitive and unaccusative verbs.

524
Verbs with a locational PP/adjunct
a. Dit is een stoeli [OPi om PRO lekker [PP in ti] te lezen].
  this  is a chair  comp  cozily  in  to read
b. Dit zijn schoeneni [OPi om PRO [PP mee ti] te dansen].
  these  are  shoes  comp  with  to dance
c. Dit is een goede omgeving [OPi om PRO [PP in ti] te herstellen].
  this  is a good environment  comp  in  to recuperate

The examples in (525) and (526) show that the construction is excluded if the adjunct PP does not allow R-extraction. First, consider (525b) which illustrates that it is not possible to strand the preposition in in the relative construction; relativization is possible but it requires that the full PP is replaced by the locational pro-form waar.

525
a. We gaan gezellig iets in dit café drinken.
  we  go  cozily  something  in this bar  drink
  'Weʼre going to drink something cozily in this bar.'
b. het caféi [waari we gezellig iets [PP (*in) ti] gaan drinken]
  the bar  where  we  cozily  something     in  go  drink
  'the bar where weʼre going to drink something cozily'

Example (526a) shows that it is not possible to have the infinitival construction with the stranded preposition, which seems to constitute additional evidence in favor of our earlier conclusion that the empty operator must be moved into clause-initial position. More surprising is that (526b) seems unacceptable as well: the most prominent, but incoherent, reading of this example seems to be the one which een café functions as the direct object of drinken'to drink'. We leave open whether the construction must be considered ungrammatical under the intended reading given that we did find a small number of examples such as this on the internet.

526
a. * Dit is een caféi [OPi om PRO gezellig [PP in ti] te drinken].
  this  is a bar  comp  cozily  in  to drink
b. ?? Dit is een caféi [OPi om PRO gezellig ti te drinken].
  this  is a bar  comp  cozily  to drink
[+]  II.  Non-restrictive infinitival clauses

Our discussion of non-restrictive infinitival clauses will be brief given that they behave in most respects similarly to the non-restrictive ones discussed in Subsection I; we will restrict our attention to a difference that seems related to the fact that, instead of restricting the denotation of the antecedent, the non-restrictive infinitival clause serves to provide additional information about the referent of the antecedent. Recall that the question marks in (527) serve to indicate that the infinitival clauses in these cases are likely to receive an appositional rather than a non-restrictive reading.

527
a. ? Deze kasteni, [OPi om PRO zelf ti in elkaar te zetten], zijn niet duur.
  these closets  comp  oneself  together  to put  are  not expensive
  'These closets, which one has to put together oneself, arenʼt too expensive.'
b. ? Dit cadeaui, [OPi om PRO ti aan Marie te geven], heb ik in Londen gekocht.
  this present  comp  to Marie  to give  have I in London bought
  'This present, meant for Marie, I bought in London.'
c. ? Zoʼn machinei, [OPi om PRO hout [PP mee ti] te schuren], is goedkoop.
  such a machine  comp  wood  with  to sand  is cheap
  'Such a machine, to sand wood with, is cheap.'

Since the antecedent of a non-restrictive infinitival clause must be identifiable independently from the information provided in the infinitival clause, these antecedents typically contain a definite determiner, like the demonstratives in (527a&b), or a type denoting expression like zoʼn'such a' in (527c); indefinite determiners or quantifiers generally give rise to a degraded result.

528
a. *? Een machinei, [OPi om PRO hout mee ti te schuren], is vrij goedkoop.
  a machine  comp  wood  with  to sand  is fairly cheap
b. *? Veel kasteni, [OPi om PRO zelf ti in elkaar te zetten], zijn niet duur.
  many closets comp  oneself  together  to put  are not expensive

Note that in examples such as (529), in which the modified noun phrase occupies the right periphery of the clause, the antecedent may contain an indefinite article. In this case, however, the om-clause is likely to be interpreted as an afterthought. This is clear from the fact illustrated in the (b)-examples that in the corresponding embedded clauses the infinitival clause cannot precede the verb in clause-final position.

529
a. Ik gaf hem een machinei, [OPi om PRO hout [PP mee ti] te schuren].
  gave  him  a machine  comp  wood  with  to sand
  'I gave him a machine, to sand wood with.'
b. dat ik hem een machine gaf, om PRO hout mee te schuren.
b'. * dat ik hem een machine, om PRO hout mee te schuren, gaf.
[+]  III.  Restrictive infinitival clauses without an empty operator

This subsection discusses restrictive infinitival clauses that do not contain an empty operator. As previously mentioned, these infinitival clauses cannot be used non-restrictively. This is illustrated here in (530).

530
a. Zoʼn machinei [om PROi hout te schuren] is vrij goedkoop.
  such a machine  comp  wood  to sand  is fairly cheap
b. *? Zoʼn machinei, [om PROi hout te schuren], is vrij goedkoop.
[+]  A.  Are non-restrictive infinitival clauses without an empty operator relative clauses?

Subsection I has argued that infinitival clauses with an empty operator are not relative clauses on the basis of the fact that they can be used predicatively, which is never possible in the case of relative clauses. This argument does not hold, however, for infinitival clauses without an empty operator, which is clear from the fact that the primed examples in (531) are not interpretable.

531
a. We zoeken een meisjei [om PROi op onze baby te passen].
  we  search  a girl  comp  after our baby  to look
a'. * Dit meisjei is [om PROi op onze baby te passen].
  this girl  is comp  after our baby  to look
b. Zoʼn machinei [om PROi hout te schuren] is vrij goedkoop.
  such a machine  comp  wood  to sand  is fairly cheap
b'. * Deze machinei is [om PROi hout te schuren].
  this machine  is comp  wood  to sand

The question as to whether non-restrictive infinitival clauses without an empty operator are relative clauses therefore cannot be decided in this way. In order to come closer to an answer, we may ask ourselves the basic question as to whether the modifying function of the infinitival clause is brought about by the coreference relation between PRO and the modified noun phrase, or whether this relation is just epiphenomenal due to the fact that often PRO must have an antecedent in order to be interpretable? If the infinitival clause is a regular relative clause we should conclude that the former is the case. However, there are examples of modifying infinitival clauses that seem to refute this hypothesis. In (532), for example, it seems clear that the infinitival clauses are used as restrictive modifiers of the noun phrase (de) tijd'(the) time'. Nevertheless, the modified noun phrase is not coreferential with PRO (nor with an empty operator, since the noun phrase does not seem to play any semantic role within the infinitival clause). These examples therefore suggest that modification by the infinitival clause is not related to the coreference relation between the modified noun phrase and PRO, which, in turn, suggests that modifying infinitival clauses are not relative clauses. More potential examples of this sort are given in (533).

532
a. Het is tijd [om PRO te vertrekken].
  it  is time  comp  to leave
b. De tijd [om PRO te vertrekken] is aangebroken.
  the time  comp  to leave  has come
533
a. Er zijn verschillende manieren [om PRO het probleem op te lossen].
  there are  several ways  comp  the problem  prt.  to solve
  'There are various ways to solve the problem.'
b. Hij toonde me de juiste manier [om PRO het te doen].
  he  showed  me  the right way  comp  it  to do
  'He showed me the right way to do it.'
[+]  B.  Restrictions on the antecedent

Whatever the correct analysis of the non-restrictive infinitival clauses under discussion is, it seems clear that they do not contain an overt relative element. It therefore does not come as a surprise that there are no restrictions on the antecedent in terms of number or gender. This is illustrated in Table 7.

Table 7: The antecedent of PRO
singular plural
non-neuter een man om het huis te schilderen
a man comp the house to paint
‘a man to paint the house’
mannen om het huis te schilderen
men comp the house to paint
‘men to paint the house
neuter een meisje om op de baby te passen
a girl comp after the baby to look
‘a girl to look after the baby’
meisjes om op de baby te passen
girls comp after the baby to look
‘girls to look after the baby’

In many cases, it is difficult to find examples in which the antecedent of PRO is inanimate, but this is due to the fact that PRO functions as the subject of an infinitival clause, and is therefore typically agentive, hence animate. However, if we are dealing with an unaccusative verb, as in (534a), or an infinitival clause in the passive voice, as in (534b), the result of having an inanimate antecedent is fully acceptable. For completeness’ sake, observe that the corresponding active construction of (534b) in (534b') involves an infinitival clause featuring an empty operator.

534
a. Dit is geen artikeli [om PROi in een taalkundig tijdschrift te verschijnen].
  this  is  no article  comp  in a linguistic journal  to appear
b. Dit is een seriei [om PROi snel herhaald te worden].
  this  is a series  comp  soon  repeated  to be
  'This is a series to be run again soon.'
b'. Dit is een seriei [OPi om PROarb snel ti te herhalen].
  this  is a series  comp  soon  to repeat
  'This is a series to run again soon.'

      Restrictive infinitival clauses without an operator are not readily used with definite noun phrases unless they are used as a nominal predicate of, e.g., a copular construction. This is clear from the contrast between the two (a)-examples in (535). The (b)-examples illustrate that a similar contrast does not arise in the case of indefinite noun phrases.

535
a. ?? De mani [om PROi het probleem op te lossen] is niet te vinden.
  the man  comp  the problem  prt.  to solve  is not to find
  'The man to solve the problem isnʼt to be found.'
a'. Jan is (typisch) de mani [om PROi het probleem op te lossen].
  Jan is typically  the man  comp  the problem  prt.  to solve
b'. Iemandi [om PROi het probleem op te lossen] is niet snel te vinden.
  someone  comp  the problem  prt.  to solve  is  not  soon  to find
  'Someone to solve the problem cannot be found soon.'
b. Jan is (typisch/echt) iemandi [om PROi het probleem op te lossen].
  Jan is typically/really  someone  comp  the problem  prt.  to solve
[+]  C.  Restrictions on the infinitive

There seem to be few restrictions on the infinitive, which is not surprising given that the antecedent is generally coreferential with the implied PRO subject of the infinitival clause. In (536a) we find an infinitival clause containing the intransitive verb werken'to work' and an implied subject PRO coreferential with the antecedent een type'a type'. Similar constructions can be found in (536b&c) with a copular and unaccusative verb, respectively. In (536d) the antecedent een machine'a machine' is interpreted as the subject of the transitive verb schuren'to sand', while in (536e), the antecedent een bedrijf'a company' is interpreted as the subject of the ditransitive verb geven'to give'.

536
a. Marie is echt een typei [om PROi te hard te werken].
  Marie is really a type  comp  too hard  to work
  'Marie is really the kind of person to work too hard.'
b. Jan is echt iemandi [om PROi gelukkig te zijn].
  Jan is really  someone  comp  happy  to be
  'Jan is really the kind of person to be happy.'
c. Dit is geen artikeli [om PROi in een taalkundig tijdschrift te verschijnen].
  this  is no article  comp  in a linguistic journal  to appear
d. Wat ik zoek is een machinei [om PROi hout te schuren].
  what  search  is a machine  comp  wood  to sand
  'What Iʼm looking for is a machine to sand wood with.'
e. Dit is echt een bedrijfi [om PROi geld aan goede doelen te geven].
  this  is really  a company  comp  money  to good causes  to give
  'This is really the kind of company that gives a lot of money to good causes.'

For unclear reasons, however, a dyadic unaccusative verb cannot be used as an infinitive in these restrictive infinitival clauses, as shown by the ungrammaticality of the examples in (537).

537
a. * Dit is een reisi [om PROi ons goed te bevallen].
  this  is a trip  comp  us  good  to please
b. * Dit plani [om PROi ons te lukken] lijkt niet te moeilijk.
  this plan  comp  us  to succeed  seems  not  to difficult
[+]  IV.  Two seemingly comparable constructions

This subsection discusses two construction types that can easily be confused with the modifying infinitival clauses in the previous subsections. The first involves infinitival purpose clauses and the second the so-called modal infinitives.

[+]  A.  Purpose clauses

Sentence-final infinitival clauses may easily be confused with adverbial purpose clauses, which may also take the form of an infinitival om-clause. A first difference between modifying infinitival clauses and purpose clauses is that the latter cannot contain an empty operator. So whereas example (538b) can be interpreted as a purpose clause, this reading is absolutely impossible in (538a).

538
We hebben de nieuwe software aangeschaft ...
  we  have  the new software  prt.-acquired
a. ... [OPi om PRO het probleem [PP mee ti] op te lossen].
  comp  the problem  with  prt.  to solve
  'We acquired the new software to solve the problem with.'
b. ... [om PRO het probleem op te lossen].
              comp  the problem  prt.  to solve
  'We acquired the new software to solve the problem.'

In (538b), however, the om-clause can still be interpreted as modifying the direct object of the main clause, nieuwe software'new software'. In this case the implied subject PRO is interpreted as coreferential with the direct object, as indicated by the coindexing in (539a); the construction can be paraphrased as “software designed to solve the problem”. On the (more prominent) purpose clause interpretation, on the other hand, the implied subject PRO is coreferential with the subject of the main clause, as indicated by the coindexing in (540a). The two structures in (539a) and (540a) differ not only in meaning, but also in syntactic behavior. First, (539a&b) show that the modifying infinitival clause can appear either in extraposed position or immediately right-adjacent to the object. The purpose clause, on the other hand, clearly prefers the clause-final position in (540a). Second, the (c)-examples show that, whereas the purpose clause can be placed in clause-initial position, the modifying infinitival clause cannot be topicalized in isolation. Finally, the (d)-examples show that only the modifying infinitival clause can accompany the direct object in clause-initial position, which of course follows from the fact that only in that case is the infinitival clause part of the direct object (the constituency test); note that we have added the adverbial phrase of time net'just' in these examples in order to facilitate topicalization.

539
Modifying infinitival clause without an empty operator
a. (?) We hebben de nieuwe softwarei aangeschaft [om PROi het probleem op te lossen].
b. We hebben de nieuwe softwarei [om PROi het probleem op te lossen] aangeschaft.
c. * [Om PROi het probleem op te lossen] hebben we de nieuwe softwarei aangeschaft.
d. De softwarei [om PROi het probleem op te lossen] hebben we net aangeschaft.
540
Purpose clause
a. Wei hebben de nieuwe software aangeschaft [om PROi het probleem op te lossen].
b. *? Wei hebben de nieuwe software [om PROi het probleem op te lossen] aangeschaft.
c. [Om PROi het probleem op te lossen] hebben wei de nieuwe software aangeschaft.
d. * De softwarej [om PROi het probleem op te lossen] hebben we net aangeschaft.

      The examples in (541) show that the infinitival clause with an empty operator in (538a) behaves just the same as the infinitival clause without an empty operator in (539): like the latter, the former can appear both in extraposed position and right-adjacent to its antecedent, and can be pied-piped by topicalization of the direct object, but cannot be placed in clause-initial position in isolation.

541
Modifying infinitival clause with an empty operator
a. We hebben de nieuwe softwareaangeschaft [om het probleem mee op te lossen].
b. We hebben de nieuwe software[om het probleem mee op te lossen] aangeschaft.
c. * [Om het probleem mee op te lossen], hebben we de nieuwe software aangeschaft.
d. De software [om het probleem mee op te lossen], hebben we net aangeschaft.

That it is indeed the presence of an empty operator that blocks a purpose reading of example (538a) can be made clear by replacing this operator by the R-pronoundaar, which would result in the structures in (542). The examples in (542) show that in this form the sentence behave just like (540). The infinitival clause clearly prefers the clause-final position, it can be topicalized in isolation (provided that the infinitival clause is assigned emphatic accent), but cannot be pied-piped by topicalization of the direct object.

542
Purpose clause
a. Wei hebben de software aangeschaft [om PROi daarj het probleem [PP mee tj] op te lossen].
  we  have  the software  prt.-acquired comp  there  the problem  with  prt.  to solve
  'We acquired the new software to solve the problem with it.'
b. *? We hebben de software[om daar het probleem mee op te lossen] aangeschaft.
c. [Om daar het probleem mee op te lossen], hebben we de software aangeschaft.
d. * De software [om daar het probleem mee op te lossen], hebben we net aangeschaft.

      To conclude this discussion, note that in copular constructions like (543a&b), the infinitival clause cannot be construed as a purpose clause, but must be construed as a restrictive infinitival clause, which is clear from the fact that the infinitival clauses cannot be topicalized in isolation.

543
a. Het zijn geen kindereni [om PROi zich gauw te vervelen].
  it  are  no children  comp  refl  soon  to bare
  'Theyʼre not children that are easily bored.'
a'. * Om zich gauw te vervelen, zijn het geen kinderen.
b. Jan is geen mani [om PROi zich twee maal te vergissen].
  Jan  is no man  comp  refl  two time  to mistake
  'Jan isnʼt the kind of man to make a mistake twice.'
b'. * Om zich twee maal te vergissen is Jan geen man.
[+]  B.  Modal infinitives

Modal infinitives, which are more extensively discussed in Chapter A9, may also occur in postnominal position. They are, however, easy to distinguish from infinitival clauses since they are never introduced by the infinitival complementizer om, and can be used both in pre- and postnominal position. Furthermore, they should not be considered as infinitival clauses but as (adjectival) phrases, just like their attributively used counterparts in prenominal position. Some examples of modal infinitives are given in (544), in which the given English translations intend to express the modal meaning of these examples: in (544a), we are dealing with the root modality of obligation or ability, in (544b) with ability, in (544c) with permission. Note the word order differences between the pre-and postnominal occurrences of the modal infinitive: in accordance with the head-final filter on attributive adjectives, the prenominal modal infinitive must be immediately adjacent to the modified noun, whereas the postnominal one may be separated from the head noun by all kinds of material.

544
a. dit [als een eerste stap in het vredesproces te beschouwen] voorstel ...
  this   as a first step  in the peace process  to consider  proposal
  'this proposal that can/must be considered as a first step in the peace process, ...'
a'. dit voorstel, als een eerste stap te beschouwen in het vredesproces, ...
b. dit [bij alle boekhandels te verkrijgen] boek ...
  this   at all bookstores  to obtain  book
  'this book that can be obtained at all bookstores ...'
b'. dit boek, bij alle boekhandels te verkrijgen, ...
c. dit soort [alleen door de overheid te gebruiken] gegevens ...
  this  kind   only  by the authorities  to use  information
  'this kind of information, which may only be used by the authorities, ...'
c'. dit soort gegevens, alleen te gebruiken door de overheid, ...

Like infinitival clauses that contain, but unlike infinitival clauses that do not contain an empty operator, modal infinitives can often be used in predicative position. The examples in (545) seem to show, however, that this is more or less restricted to those cases in which the modal infinitive expresses ability.

545
a. Dit voorstel is te beschouwen als een eerste stap in het vredesproces.
  this proposal  is to consider  as a first step in the peace process
  'This proposal can to be considered as a first step in the peace process.'
b. Dit boek is te verkrijgen in alle boekhandels.
  this book  is to obtain  in all bookstores
  'This book can be obtained in all bookstores.'
c. ?? Dit soort gegevens is alleen door de overheid te gebruiken.
  this kind information  is  only  by the authorities  to use

      As is indicated in (544) by means of the use of commas, postnominal modal infinitives are (in contrast to the prenominal ones) most readily interpreted non-restrictively. The examples in (546) serve to illustrate the difference between the postnominal modal infinitives and non-restrictive infinitival clauses by means of a minimal pair: the infinitival clause in (546a) gives the additional information that the bookcases are not yet assembled but that the customer should do that himself; the modal infinitive in (546b), on the other hand, conveys the information that bookcases are such that the customer is able to put them together himself.

546
a. Deze kasten, om zelf in elkaar te zetten, zijn niet al te duur.
  these closets  comp  oneself  together  to put  are  not  very expensive
  'These closets, which one has to put together oneself, arenʼt too expensive.'
b. Deze kasten, zelf in elkaar te zetten, zijn niet al te duur.
  these closets  oneself  together  to put  are  not  very expensive
  'These bookcases, which one can put together oneself, arenʼt too expensive.'

The examples in (547a&b) show that postnominal modal infinitives can sometimes at least marginally be used restrictively provided that the phrase headed by the modal infinitive is complex; if it is not, the modal infinitive must be in prenominal position. In this respect, modal infinitives behave just like non-restrictive adjectival phrases; cf. Section 3.3.5.

547
a. Rekeningen [*(?door ons) te betalen] moeten eerst gecontroleerd worden.
  bills         by us  to pay  must  first  checked  be
  'Bills to be paid by us have to be checked first.'
a'. (Door ons) te betalen rekeningen moeten eerst gecontroleerd te worden.
b. De rekeningen [te betalen *(?voor de 15e)] heb ik apart gelegd.
  the bills   to pay    before the 15th  have  separate  put
  'The bills to be paid before the 15th Iʼve put aside.'
b'. De (voor de 15e) te betalen rekeningen heb ik apart gelegd.
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