We need to distinguish between finite and infinitival argument clauses. The examples in (16) show that the choice depends on the matrix verb: while propositional verbs like zeggento say or bewerento claim can take either a finite or an infinitival clause, an irrealis verb such as proberento try is only compatible with an infinitival clause. Note that we assume that the infinitival clauses in the primed examples contain a phonetically empty pronominal element PRO, which functions as the implied subject of the infinitival clause; we will discuss this element in more detail in Section 4.3.

Replacing finite interrogative clauses with infinitival ones does not always seem to be possible. Although example (17a') is acceptable, it belongs to a more formal register; in colloquial speech we only find more or less fixed forms such as Hij vroeg me wat te doenhe asked me what he should do, and Vos (1994:148) shows that such infinitival clauses are also common as independent expressions, e.g. in instructions such as Wat te doen in het geval van brandWhat to do in case of fire, or as rhetorical questions. Example (17b') is also acceptable, but the verb introduces a request, rather than a question.

That the verb determines the form of the argument clause is also clear from the examples in (18), which show that while perception verbs such as ziento see can take either a finite or an infinitival complement clause, the causative/permission verb laten only allows infinitival clauses.

A comparison of the primed examples in (18) with those in (16) shows us that the verb also determines the type of infinitival clause; while the verbs in (16) take te-infinitivals, the verbs in (18) take bare infinitivals (i.e. without te). Section 5.2 will provide a brief introduction to the different types of infinitival clauses.

There seem to be only few verbs that can be combined with a finite but not with an infinitival declarative object clause. Manner of speech verbs seem to prefer a finite clause as their complement, but judgments about the corresponding infinitival constructions seem to vary from case to case and from person to person. This is also evident from a Google search (3/16/2012) on the string [Vfinite * te zullen] for various tense forms of the matrix verbs roepento call, schreeuwento yell and huilento cry. While there are many examples of these verbs with a finite declarative clause, our search yielded only a small number of cases in which they were followed by an infinitival clause. We found a relatively large number of examples such as (19a') with the verb roepen, but only two examples such as (19b') with the verb schreeuwen, and no examples such as (19c') with the verb huilento cry. Nevertheless, all the primed examples seem to be passable for at least some of the speakers we consulted.

At first glance, the (a)-examples in (20) seem to contradict the claim that there are few verbs that can be combined only with a finite declarative clause, but the (b)-examples show that we should be careful not to jump to conclusions.

The contrast between the two primed examples seems to be related to the preferred interpretation of the implied subject PRO of the infinitival clause. First, consider the primeless examples with a finite clause: the most prominent reading of (20a) is that Jan noticed or discovered something about someone else, i.e. the subject pronoun hijhe of the embedded clause is preferably interpreted as referring to a person not mentioned in the sentence; example (20b), on the other hand, is also compatible with a reading in which Jan noticed or discovered something about himself, i.e. in which the subject pronoun hij takes the subject of the matrix clause as its antecedent. The contrast between the primed examples can now be explained by referring to the fact that the implied subject PRO of the infinitival clause differs from the subject pronoun hij in that it must be interpreted as coreferential with the subject of the matrix clause. This makes the interpretation of (20a') as unusual as that of (20a) in the reading in which the pronoun hij is taken to be coreferential with the subject of the matrix clause. See Section 4.3 for a brief introduction to the restrictions on the interpretation of the PRO-subject of infinitival argument clauses.

It seems that, besides the restrictions imposed by the interpretation of PRO, there are several other factors that can affect the acceptability of infinitival argument clauses. For instance, the examples in (21) suggest that the verb voorkomento prevent can only select finite clauses; the pronoun hij in the (a)-examples can easily be interpreted as coreferential with the subject of the main clause, but nevertheless the primed examples are severely degraded.

The examples in (22), on the other hand, show that the primed examples improve a greatly when we add an adverbial phrase indicating causality or manner.

The primed examples in (23), which are adaptations of sentences found on the internet, further show that such examples become even better when the embedded clause is a passive or copular construction. Note that the relevant issue is not that the subjects of passive and copular constructions are internal arguments, since the same applies to the subjects of unaccusative verbs such as vallento fall in the marked (b)-examples above.

Although there are other possible problems with the claim that there are few (if any) verbs that can be combined with a finite but not an infinitival declarative clause, we will conclude by pointing out one last case, viz. the contrast between the two examples in (24). The reason why (24a) has no infinitival counterpart may simply be that it is an idiomatic expression (listed as such in dictionaries); the possibilities for substituting the finite clause in (24a) are very limited.

The examples in (25) suggest that there are also few verbs that can be combined with a finite but not with an infinitival prepositional object clause: the (a)-examples show that verbs such as verwachtento expect, which normally take finite PO-clauses, also allow infinitival complements. On the other hand, verbs such as vragento request, which normally take infinitival PO-clauses, yield a degraded result with a finite complement clause.

To our knowledge, the factors affecting the acceptability of infinitival argument clauses have not been studied in detail, but we tentatively conclude, on the basis of the discussion above, that verbs that select a finite declarative argument clause can usually also take an infinitival clause, but not necessarily vice versa. Future research will have to show whether this conclusion is tenable.