The indefinite noun phrase in an expletive construction can either be specific or nonspecific. The most plausible reading of (72a) is the one where the speaker is not able to identify the person in question, whereas the most plausible reading of (72b) is that at least the speaker is able to identify the person in question in discourse. These examples also show that the nonspecific indefinite noun phrase in (72a) must follow the adverb, that is, cannot be scrambled. The specific one in (72b), on the other hand, can more readily be placed in the position in front of the adverb, which indicates that it can at least marginally be scrambled. In the case of a quantifier like iemand'someone' in (72c), scrambling is even the normal means to make the distinction between the two interpretations: if the quantifier follows the adverb, it is preferably construed as nonspecific, whereas it must be construed specifically if it precedes it.

      The examples in (73) show that the nonspecific indefinite noun phrase is not commonly used without the expletive, whereas the specific one can be used without the expletive. For completeness’ sake, note that we have put aside the fact that in some varieties of Dutch, examples such as (73a) are also acceptable without the expletive; we are only discussing the varieties here that do not allow this.

It should be noted, however, that the expletive is sensitive not only to the type of its subject, but also to the presence or absence of some presupposition in the clause; cf. Bennis (1986). Consider the examples in (74). In (74a) the adverbial phrase voor mijn huis follows the indefinite subject and is construed as part of the focus of the clause: since there is no other presupposition, the expletive must be realized. However, if the adverbial phrase precedes the subject, it can (but need not) be construed as the presupposition of the clause; if it is, the expletive may be dropped.

Something similar can be observed in (75). Although for some unknown reason (75a) is perhaps somewhat marked on a nonspecific interpretation of the subject, it seems that this reading does require the expletive to be present, which is consistent with the fact that the object is preferably interpreted as a nonspecific indefinite noun phrase. In (75b), which may again be somewhat marked on a nonspecific interpretation of the subject, the expletive can be readily left out; this is related to the fact that the definite object het boek can (but need not) be interpreted as part of the presupposition of the clause. In (75c), which readily allows a nonspecific interpretation of the subject, the expletive cannot be used, which is due to the fact that the object pronoun het must be construed as part of the presupposition of the clause; see Broekhuis (2007/2008) for more discussion.

      From the data in (73) to (75), we may conclude that, in the absence of a presupposition, the expletive must be realized if the subject is nonspecific. An exception must be made, however, for nonspecific indefinite noun phrases modified by certain attributive adjectives or restrictive relative clauses. The primed examples in (76) show that they can be placed in the regular subject position, that is, the position occupied by the expletive in the primeless examples. Probably, the attributive adjective/relative clause makes the noun phrase sufficiently specific to occupy this position.

The examples in (77) show that modified noun phrases are even preferably placed in the regular subject position if the clause contains sentential negation. Note that these examples should not be confused with examples such as Er is een tachtig jaar oude man niet goed geworden'An eighty year old man became unwell', where the negative adverb is construed with the adjectival predicate. In these cases we are probably dealing with constituent negation (niet goed'not well' ≈ onwel'ill').

      A second exception involves examples in which the head of the indefinite subject receives contrastive accent. So whereas an indefinite subject like een man in (78a) normally cannot occur without the expletive, it can occur without it if the noun man is contrastively stressed, as in (78a'). If the noun phrase contains a numeral or quantifier, as in (78b), the expletive may also be dropped if contrastive accent is assigned to the numeral/quantifier, although in this case the noun phrase is likely to receive a partitive reading; cf. De Hoop (1992).

That nonspecific indefinite noun phrases are normally preferably introduced by an expletive is also clear from the fact that such noun phrases may invoke special semantics when they occur in the regular subject position. Consider the (a)-examples in (79). Example (79a) merely claims that some student was arrested. If the indefinite noun phrase is placed in regular subject position, the indefinite article is preferably stressed so that we cannot immediately observe whether we are dealing with the article or the numeral één 'one' . The preferred reading of the primed example is a partitive one: it is claimed that a certain student from a contextually determined set of students was arrested — the interpretation of the indefinite noun phrase comes rather close to één van de studenten 'one of the students' ; cf. Section 4.1.1.6, sub I. The (b)-examples in (79) show that the same phenomenon can be found in cases that unambiguously involve a numeral or a quantifier.

As we noted above, it cannot be immediately be observed whether we are dealing in (79a') with the indefinite article or the numeral één'one'. The fact illustrated in (80) that the indefinite plural noun phrase studenten cannot occur in the regular subject position suggests the latter. This supports our earlier conclusion that unmodified nonspecific indefinite noun phrases normally cannot occur in regular subject position.

A further difference between the expletive construction and the construction with the indefinite noun phrase in the regular subject position is that the noun phrase can never be interpreted generically in the former. Consider the examples in (81): the indefinite noun phrase in the expletive construction in (81a) cannot be interpreted generically, whereas example (81b) must be construed generically. The difference can be made clearer by putting the examples in the past tense: (81a') is still acceptable and expresses that it used to be the case that some hippo was lying in the water; (81b'), on the other hand, is weird since it suggests that hippos in general have changed their habit of normally lying in the water. Note that (81b') becomes acceptable on a specific or partitive interpretation if we stress een: it used to be the case that a certain hippo or one of the hippos was lying in the water.

The examples in (82) show that the same pattern arises in the case of plural indefinite noun phrases. Again, the primed (b)-example is unacceptable due to non-syntactic factors, given that it suggests that hippos in general have changed their habit of normally lying in the water.

Summarizing, we can say that (unmodified) nonspecific indefinite subjects introduced by the indefinite article een/∅ must normally be part of an expletive construction. Specific indefinite subjects, on the other hand, may either be part of an expletive construction or occupy the regular subject position. Indefinite subjects with a partitive or generic interpretation, finally, cannot occur in an expletive construction but must occupy the regular subject position.

      To conclude this section on the expletive construction we want to mention that narratives pose an exception to the general rule that nonspecific indefinite noun phrases headed by an indefinite article do not occur in the regular subject position. A story might well begin as in (84), where the function of the noun phrase een man is clearly to introduce some new discourse entity without the implication that the speakers would be able to uniquely identify the intended referent. The sentence in (84) is acceptable only if the discourse is continued with a story about this person sitting in the waiting room.