Non-finite verb forms can also be used as noun-terms to form subject, direct object, indirect object and adverbial components. As such they can also be strung together to create verb chains. This is probably one of the most, if not the most, complex structure in the syntax of the English language. The following table outlines the high-level possibilities.
Infinitives as Noun-terms
Non-finite verb forms can be used extensively as elements of the subject, complement, object and adverbial components. Infinitives, passive infinitives and verb chains cannot be used in preposition phrases headed by by or through, so they cannot be used in the passive equivalent with a transitive verb to indicate the agent that was the subject in the active voice. There is one instance where they can be used in adverbials which is as part of prepositional phrases such as in order to do something.
Infinitives can form either the subject or the complement of a copula statement.
Infinitives can’t form the subject of an intransitive verb. The reason is that in an intransitive statement the subject is what gets modified in the course of the event and, by their nature, infinitives aren’t modifiable. There cannot be degrees or modes of an infinitive.
The infinitive can form the subject of a transitive verb in both the active and the passive voices and also the direct object but not, unlike a gerund, the indirect object.
Furthermore, when a passive equivalent is formed the subject cannot be optionally included in a prepositional phrase. Instead a gerund would be substituted. For example, the statement to speak the words represents progress in the active voice would become progress is represented by speaking the words in the passive voice equivalent as we can’t say *progress is represented by to speak the words. Although there is a certain level of interchangeability between infinitives and gerunds, in some cases only the gerund can be used.
However, where the infinitive forms the direct object, it is possible to form a passive equivalent with the infinitive as the subject.
Gerunds
A gerund is the present participle of a verb used as a noun. Although in many cases inter-changeable, gerunds can be used more widely than infinitives and may be qualified by determiners and adjectives in the same way as common nouns.
However, one limitation is that gerunds can’t have a continuous aspect. The reason is that the continuous aspect is formed from the present participle of the auxiliary verb to be and the result would therefore be an unnecessary and unidiomatic form such as *our being talking or *their being speaking the words; unnecessary because our talking and our speaking the words will do the job and the sounds flow much more easily.
Gerunds can function as both subject and complement with a copula. Note that as a complement, us sounds better than our, as pronouns take the object form in complements.
Gerunds can also function as the subject of an intransitive verb but only in the simple basic form. The compound forms are not possible. The continuous aspect is excluded for the reason noted above and the perfect and continuous perfect are excluded because the perfect implies completion and the subject of an intransitive verb can be modified in the course of an event. So, while our running can be the subject of an intransitive verb, our having run and our having been running are completed events that cannot be changed in the course of the event being described and therefore cannot be the subject of an intransitive verb. There are exceptions but they would have to be contrived. For example, with the verb to exist; we could say our having existed changed the course of events or our having been existing was significant.
Gerunds can function as the subject, direct object and indirect object of a transitive verb. Because they can be part of a prepositional phrase in an adverbial component, the passive voice equivalent is also possible.
Interestingly, a gerund is usually qualified by an adverb rather than an adjective. This suggests it retains the verb meaning even when used as a noun.
As a verb, the phrase would be we are attending reluctantly with the qualification coming from an adverb. Turned into a noun, a gerund should be qualified by an adjective. However, this seems to be possible only in the non-compound form. What seems to be happening is that the present participle and the adverb are treated as a unit when the phrase is re-constructed as a gerund.
Passive Infinitives as Noun-terms
Past participles can be used with the infinitive to form the passive infinitive.
The passive infinitive can be used as the subject of a transitive verb except in the perfect continuous aspect. This is because, as noted above with regard to infinitives, the perfect continuous doesn’t function because there is a conflict between the been of the perfect and the being of the passive, so that *to have been being allowed isn’t possible. As with other infinitives, the passive equivalent cannot be formed because a passive infinitive cannot be part of a prepositional phrase.
It should be noted that there a counter-intuitive combination of active and passive voices in this construction. The verb in the statement is in the active voice while the subject of the verb is in the passive.
Passive infinitives can also be used as direct objects of transitive verbs and as subjects in the passive equivalent. It should be said that the more complex forms, while syntactically possible, are on the borders of intelligibility and the statements should probably be re-cast.
Verb chains as Noun-terms
There is one further complexity to the use of non-finite verb forms in noun-terms and that is the possibility of verb chains.
Simple verb chains have just two elements which combine one of these ideas with a verb in the infinitive but three elements are not unusual and even a chain with four elements is possible. For example, you could say we expected to continue to be allowed to travel using our old passports. More than four elements will tend to become unwieldy.
As in other circumstances, there is a level of interchangeability between infinitives and present particles. You might say either we expected to continue to travel or we expected to continue travelling. Sometimes there may be a different meaning; for example, we forgot to pay for it doesn’t mean the same thing as we forgot paying for it. Similarly, although we can either expect to continue being something or expect to continue to be something, we would have to continue to expect to be something.
The type of the verb constrains how a chain can be built. Generally, verb chains can include copulas, intransitive verbs and transitive verbs. However, the rules about complements and objects still apply.
A copula must have a complement. This presents no difficulty because infinitives and gerunds can function as noun-terms and can therefore function as complements. It is therefore possible to have a string of copula verbs.
Similarly, A transitive verb must have at least one object in the active voice and may have one object in the passive voice. Again, this presents no difficulty as infinitives and gerunds are noun-terms and can function as objects, so it is possible to have a string of transitive verbs.
However, because an intransitive verb cannot have an object, intransitive verbs can only be the last element in the chain, as what follows must be an adverbial. For example, the intransitive infinitive to travel must be followed by an adverbial, either an adverb such as hopefully or a prepositional phrase such as in order to do something, and both of these break the chain.
The next table shows how each element is constructed.
These elements can then be used as units in a chain of verbs. The next two tables show a simple structure with a single infinitive as the complement of a copula verb and object of a transitive verb.
It then becomes possible to create a longer chain of verbs. Note that it is possible in an adverbial to start another chain.
There are a number of verbs that particularly lend themselves to verb chains as they modulate the state or event that is being described.
