60. Purpose Sentences with “For”

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Running FOR Victory

The word “for” acts differently in different kinds of purpose sentence, and sometimes causes errors as a result

THE PROBLEM POTENTIAL OF PURPOSE-SHOWING “FOR”

Purpose sentences often contain the preposition for. However, there are some rather confusing rules concerning this word in purpose sentences, and as a result some common errors made with it. A particularly noticeable error is combining for with an -ing verb, like this: 

(a) *Afterwards the dancers go off for enjoying themselves. 

Although an -ing verb can sometimes be used after for to express a purpose, it cannot in this example sentence (see 165. Confusions of Similar Structures 2, #3). Possible corrections include to enjoy, in order to enjoy or so that they can enjoy. In this post I wish to examine exactly when you can and cannot use for in a purpose sentence.

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THE BASIC FEATURES OF PURPOSE SENTENCES

Purposes are future events or situations that living creatures seek to achieve by doing something. Consider these examples: 

(a) Doctors STUDY anatomy so that they MAY UNDERSTAND sickness.

(b) Colleges TEACH anatomy so that doctors WILL UNDERSTAND sickness. 

The underlined words are purposes. The living creatures that want to achieve them are doctors in (a) and colleges in (b). The things being done to achieve the purposes – what we might call the “means” of achieving them (see 73. Prepositions for Saying How) – are shown within the words that are not underlined. 

In these examples, the purpose and a means of achieving it are expressed with separate verbs, though elsewhere one or both may be a noun (see 81. Tricky Word Contrasts 2, #3 and 119. BE before a “to” Verb, #1). With two verbs, their subjects may represent the same idea – “doctors” in (a) – mention of the second being with a pronoun (they); or they may represent two different ideas: colleges and doctors in (b).

The words so that before the purpose in (b) are a conjunction: they allow the two verbs to be in the same sentence (see 230. Multi-Word Conjunctions). An alternative purpose conjunction is the slightly more formal in order that. With these conjunctions, the purpose verb must usually contain can, will or may or their “past” equivalents could, would or might (see 32. Expressing Consequences).

Three other synonyms of so that are to, in order to and so as to. However, because they have to instead of that, their following verb cannot contain may etc. (see 231. Confusions of Similar Structures 3, #3). They also need their subject to be expressed differently. Compare:

BOTH SUBJECTS THE SAME WITH “to”

(c) Doctors study anatomy (in order/so as) to understand sickness. 

Here, the repeated subject is left out – using they is not possible.

BOTH SUBJECTS DIFFERENT WITH “to”

(d) Medical colleges teach anatomy (in order) for doctors to understand sickness. 

In this case, the different second subject (doctors) has to be mentioned. It needs for because the verb has to. Note that so as to cannot replace to.

The use of for in (d) illustrates what is probably its most important one in purpose sentences. It can be summed up like this: 

1. For and its noun go directly before to.

2. The noun expresses the subject of the to verb, not the purpose itself.

3. The to verb’s subject is not the same as the other verb’s subject.

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OTHER USES OF “for” IN PURPOSE SENTENCES

In other uses, for is more associated with the purpose itself than its subject. There are two main kinds of use: with a noun and no verb after for, and with a verb and no noun (a noun and verb together can only be the use described above).

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1. “For” + NOUN meaning “in order to have”

English quite often uses for + NOUN to mean either “in order to obtain”, “in order to receive” or “in order to have”. In these cases, the noun after for shows what the purpose holder wants to possess or achieve. Here are some examples: 

(e) Students have to work hard for good grades.

(f) The patient needs to return to the clinic for a reassessment.

(g) For a full explanation, please turn to page 6.

(h) It is healthy to go for regular walks. 

Although no verb is present among the purpose words in such sentences, the “have” meaning of for ensures a verb idea is still present.

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2. “For -ing” meaning “in order to do” (after certain verbs only)

Expressing “in order to do” with for -ing only seems possible when the main verb in the sentence is one of a small group, a common example being USE. Here is a typical purpose sentence containing USE:

(i) An ammeter is used for measuring electric current.

Instead of an -ing verb after for, one could also use an “action” noun (for the measurement of… – see 131. Uses of “Action” Nouns). The passive form (is used) seems especially common in such sentences, but the active is certainly possible too (e.g. We use an ammeter…).

Other verbs which allow for -ing meaning “in order to do” are HAVE, KEEP, NEED and ALLOW, as well as their synonyms (e.g. POSSESS, MAINTAIN, STORE, REQUIRE and PERMIT). Adjectives related to them can also be used in combination with BE, common examples being useful, of use, valuable, helpful, good, suitable, necessary, optional, requisite, important, vital, essential, crucial, compulsory and mandatory.

It is this restriction on the verbs usable with for -ing that makes sentence (a) above incorrect: the verb GO there is not one of the allowed kind. GO seems to be a verb that is particularly often used in this erroneous way, perhaps because it can separately combine with either for or -ing (see 176. Ways of Using GO). DO SOMETHING is another verb that is often incorrectly combined with for -ing.

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A NON-PURPOSE USE OF “for -ing”

If for -ing is not used with the above verbs, it will either sound incorrect or express a function rather than a purpose. Functions name what something does, rather than what people hope it will do (see 119. BE Before a “to” Verb, #2). Consider this:

(j) Chlorophyll in plants is for utilizing solar energy.

Chlorophyll here is not consciously trying to perform its function.

The function and purpose uses of for -ing are recognisable from their grammar as well as their meaning. The function usage tends to act like an adjective in sentences, the purpose one an adverb. Adjective-like uses describe a preceding noun while adverb-like ones say something about a verb (see 84. Seven Things to Know about Prepositions, #2).

In sentence (i) above, for example, for measuring… is describing the verb is used and is hence adverb-like and purpose-naming. In (j), however, for utilizing… is describing the noun chlorophyll and is hence adjective-like and function-naming. This particular adjective-like use is separated from its noun by the verb BE. In other cases, however, the noun and for -ing might be together:

(k) The form has a SPACE for giving extra information.

This names the function of the mentioned space.

In the following example, things are slightly more complicated:

(l) The company provides BUSES for transporting its employees.

Does this name the purpose of the company or the function of buses? Grammar is of less help here because the preposition phrase could be either adjective-like or adverb-like: it could be linking with either the verb provides or the noun buses (see 124. Structures with a Double Meaning 1, #2). However, there is still a clue that the use is adjective-like and function-describing: provides is not one of the above-listed verbs that allow a purpose to be described with for -ing. In order to express a purpose, for would need to be used in the first way described above: for + noun + to… (…for its employees to be transported in).

Note that some noun functions can also be expressed with a to verb. This is not possible in (k) (space to give there would be an abbreviation of space for people to give – a purpose statement), but one could write buses to transport in (l) (see 239. Noun Phrases Made with a “to” Verb). The reason for the difference is that space in (k) is not the subject of the verb after it (GIVE), but buses in (l) could be. A problem with saying to transport after buses in (l), however, is that two alternative understandings would be possible: it could express the purpose of the company as well as the function of buses.

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PRACTICE EXERCISE: “for” IN PURPOSE SENTENCES

Readers wishing to test their understanding and memory of the points above may like to try the following small exercise. The sentences must be judged as grammatical or ungrammatical purpose statements, and corrected where necessary. Suggested answers are given afterwards.

1. Drivers look at a speedometer for knowing how fast they are travelling.

2. Headlamps should be switched on for the vehicle to be visible in fog.

3. It is sometimes wise to sound the horn for safety before a bend.

4. For preventing evaporation, the fuelling pipe needs a cap.

5. Cars have indicators for the driver giving warnings.

6. Switch on the air conditioning for travelling in comfort.

7. For journeys without stress, cruise control is available.

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Suggested Answers

1. Rewrite for knowing as (in order) to know (for + -ing is not possible with the main verb look at).

2. No change (for+ SUBJECT + to+ PURPOSE VERB).

3. No change (for + NOUN = “in order to obtain”).

4. No change (for + -ing with acceptable verb needs).

5. Either delete the driver so as to leave for + -ing after HAVE, or rewrite giving as to give to make for + NOUN + to.

6. Rewrite for travelling as (in order) to travel (for + -ing is not possible with the main verb switch on).

7. No change (for + NOUN = “in order to obtain”).