Placing “is” (or other form of BE) directly before a verb with “to” can express various meanings
GRAMMAR FORMS AFTER be
Verbs with “to” – infinitives – are not the most typical grammatical forms found after the verb BE. Much more common are participles (where BE is an auxiliary verb), nouns (or their equivalents) and adjectives (see 3. Multi-Use Words). However, there are at least eight different meanings that an infinitive can express when placed after BE. Some are possible with all forms of BE, while others go with only some. In this post I wish to present and compare the different meanings that an infinitive can have in English when placed after BE.
A reader of this blog once asked for a complete survey of infinitive usage in English. Unfortunately, this is not possible because it would not meet the Guinlist objective of seeking to explain what is absent from mainstream grammar descriptions. However, quite a range of information about infinitives can still be obtained from this and various other posts. Interested readers are referred to 35. “To Do” versus “To Doing”, 60. Purpose Sentences with “For”, 78. Infinitive versus Preposition after Nouns, 83. Active Verbs with Non-Active Meanings 2, 103. Using “it” for a Subsequent Verb, 105. Questions with a “to” Verb and 148. Infinitive Verbs without “to”.
INFINITIVES THAT MAY FOLLOW ANY FORM OF be
Most of the infinitive meanings are in this category. Each seems recognizable mainly from the words used before BE.
Examples of this use are:
(a) The purpose of speed cameras is to prevent road accidents.
(b) The prize is to attract more people.
In the first of these, the subject of BE includes the word purpose, thus leaving no doubt that the infinitive also has that meaning. Synonyms like aim, intention, objective, plan and target are also possible. Sentence (b), on the other hand, shows that such a word is not always necessary. The idea of purpose can seemingly still be understood purely on the basis of world knowledge – in this case the common observation that attracting more people is a frequent purpose of a prize. The importance of world knowledge for recognising meanings is indicated elsewhere within this blog in posts like 18. Relations Between Sentences and 107. The Language of Opinions.
Nevertheless, the absence of any specific language to indicate the meaning of purpose can, given the existence of other possible meanings of BE TO, create double meanings. Sentence (b) could, for example, be understood as saying that attracting more people was the prize itself rather than its purpose (see category 6 below). For more about double meanings, see 124. Structures with a Double Meaning.
Functions are very like purposes but not exactly the same. They are similar in being outcomes, but they are more like facts than hopes or desires (see 60. Purpose Sentences with “For”). A typical function sentence might be:
(c) The function of chlorophyll is to convert inorganic substances into organic ones.
Chlorophyll here does not try to do what it does; it just does it. Contrast this with sentence (a), where the subject speed cameras is also non-living, but the outcome is very much a human desire.
Function statements do not always have to have a non-living subject. Consider this:
(d) The function of doctors is to cure or alleviate human sickness.
The meaning here is different from what it would be with function replaced by purpose: information is given about what doctors normally do but not about what doctors themselves are trying to achieve – their purpose. This might be the same as their function, but it could also be completely different – to have a comfortable life, for example, or to be popular.
Function statements with BE TO seem to need a word like function or role near the start to assist their recognition.
A means is an action undertaken in order to achieve a purpose. It is the usual meaning of by before an -ing verb (see 73. Saying How with “By” and “With” and 101. Add-On Participles). A to verb becomes an alternative in sentences like the following:
(e) The best way to learn a language is to live amongst its speakers.
It would also be correct here to say by living. The key requirement for making BE TO means-naming seems to be having the word way (or, rarely, a synonym such as method) as subject.
An arrangement is a future plan that has been agreed by two or more people. It may or may not involve the person reporting it. It can be expressed using BE TO like this:
(f) A meeting of finance ministers is to be held in Brussels.
(g) The armies were to converge on the plain at midday.
The arrangement may be for the actual future, as in (f), or for one in the past, as in (g). BE TO is not the primary way of expressing arrangements – putting the other verb into the present continuous tense (is being held and were converging above) seems more common (see 147. Types of Future Meaning). With BE TO there is a suggestion that the mentioned people are not the primary makers of the arrangement, but still have contributed enough to rule out the use of HAVE TO (see 129. Differences between Necessity Verbs).
Occasionally arrangement-reporting is little different from a command. Consider this:
(h) All visitors are to report to Reception.
This command could also be given with must. I would suggest that are to is preferred because it sounds more polite: it makes the necessity of the action seem to be a result of communal agreement rather than somebody’s directive.
The main clues to the existence of arrangement-reporting with BE TO seem to be (I) the absence of a word like purpose, function or way in the subject of the sentence, (II) ability of the subject to carry out the infinitive verb’s action, and (III) ease of arranging the infinitive verb’s action. Sentences (f), (g) and (h) meet all of these conditions. Sentences (b) above and (m) below fail on (III) (attracting people and becoming an emperor are not easily arranged), while (k) below fails on (II) (a prize cannot usually meet people).
Sentences of this kind have an infinitive verb before BE as well as after:
(i) To think is to exist.
The meaning of the subject of (i) (to think) is not being identified or clarified by the later infinitive in the way discussed in the post 117. Saying More Precisely What You Mean. Instead, a consequence of it is being indicated by the later infinitive: (i) could be paraphrased as If you think, you exist. Here is a further example:
(j) To climb Everest is to join a very select group.
In this use, the to verb simply spells out in more detail what the subject of the verb represents: the sentence is of the kind that is considered in detail in the post 117. Saying More Precisely What You Mean. The previously-considered uses of BE + to for naming a purpose, function or means are really just subdivisions of this wider category. The subject of the verb needs only to stand for an action of a very general kind, like this:
(k) The prize is to meet a famous actor.
In general usage, the word prize does not necessarily represent an action, but it can – and it does so here. The to verb specifies the action that the prize is. Other very general action-indicating nouns that a to verb could specify include challenge, effect, next step, outcome, possibility, problem, procedure and task. In contrast, meeting in (f) is a less general action, and armies in (g) is not an action at all.
INFINITIVES THAT FOLLOW A SPECIFIC FORM OF be
Two common meanings in this category are what I call unlikely future and destiny in the past.
1. Unlikely Future
This is the use of were to after if (see 118. Problems with Conditional “if”), as in sentences like this:
(l) If aliens were to visit the earth, great excitement would prevail.
The suggestion here is that the future arrival of aliens is unlikely. Likely futures need the present simple tense after if, and will with the other verb. The word were is the only form of BE allowed in the unlikely future use, even when its subject is singular. The reason is that it is not the usual were but the special one known as the “subjunctive”, which never changes.
2. Destiny in the Past
This kind of sentence also needs a past tense form of BE, e.g.:
(m) Augustus was to become Roman Emperor six years later.
The infinitive here indicates a future life event – destiny – of a person or thing in the past (the subject of the sentence). There is a resemblance to sentences like (g), where the future event is an arranged plan. As mentioned above, however, this latter meaning is unlikely in (m) because arranging to become an emperor is not easily done by ordinary people, especially six years beforehand.