8.38 necessary conditions

If you want to say that one situation is necessary for another, you use 'provided', 'providing', 'as long as', 'so long as', or 'only if'. 'Provided' and 'providing' are often followed by 'that'.

• A child will learn what is right and what is wrong in good time --- provided he is not pressured.
• Lady Sackville was prepared to come, provided that she might bring her daughter.
• The oven bakes magnificent bread providing there is a hot enough fire in the furnace.
• They are content for the world to stay as it is, poverty, pain and everything, as long as they are comfortable.
• These activities can flourish only if agriculture and rural industry are flourishing.

When you are using 'only if', you can put the 'only' in front of the verb in the main clause. For example, instead of saying 'I will come only if he wants me', you can say 'I will only come if he wants me'.

• He told them that disarmament was only possible if Britain changed her foreign policy.

Another way of saying that one situation is necessary for another is to use a conditional clause beginning with 'if' followed by a noun group as subject, 'be', and a 'to'-infinitive clause. In the main clause, you say what is necessary using 'must'.

• It's late, and if I am to get any sleep I must go.
• If you are to escape, you must leave me and go on alone.

8.39

If you want to say that one situation would not affect another, you can use 'even if'.

• I would have married her even if she had been penniless.
• Even if you've never been taught to mend a fuse, you don't have to sit in the dark.
• Even if we do not resort to such dramatic measures, it seems likely that there will be many exciting opportunities in the future.

'Even if' is also used in concessive clauses. This is explained in paragraph 8.67.

8.40

If you want to say that a situation would not be affected by two or more things, you use 'whether'. You put 'or' between the different possibilities.

• If the lawyer made a long, oratorical speech, the client was happy whether he won or lost.
• Catching a frog can be a difficult business, whether you're a human or a bird or a reptile.
• Whether you go to a launderette or do your washing at home, the routine is the same.

If you want to say that what happens would not be affected by either of two opposite situations, you use a clause beginning with 'whether or not'.

• Whether or not people have religious faith, they can believe in the power of love.
• I get an electrician to check all my electrical appliances every autumn, whether or not they are giving trouble.

The 'or not' can be put at the end of the clause.

• Whether I agreed or not, the search would take place.