Строй современного английского языка

ON GRAMMATICAL STATEMENTS
As the teaching of a language to foreigners requires the formulation of rules which the learner has to observe if he is to speak and write the language correctly, practical grammars, written both by speakers of the language in question and by foreigners, tend to be excessively strict in laying down what is "inadmissible" in the language. Numerous specimens of exaggerations may be found practically in every grammar book.
Let us consider a few of the most characteristic examples of such exaggerations.
It is frequently laid down as a rule that verbs of perception, such as see, hear, feel (in the meaning 'experience'), also those denoting emotions, such as love, like, hate, etc., cannot be used in any of the continuous forms.
This rule, thus bluntly formulated, is not borne out by actual usage. All of these verbs can, under certain circumstances, be used in the continuous forms though of course they are less commonly used in these forms than, say, verbs of physical action, such as walk, beat, strike, jump, run, etc., or verbs of position in space, such as stand, sit, lie, hang, kneel, etc. To be sure, was seeing is a much rarer form than was running. And yet was seeing is not impossible, nor is was hearing, was liking, etc., and also was being, e. g.. in the sentence He was being polite to you. In a similar way, the verb feel can be used in the continuous form, as for instance in a question addressed to a sick person: Are you feeling better to-day?
Another example of a rule formulated too bluntly is that about the use of tenses in a conditional if-clause. It usually runs something like this: "In a conditional if-clause the present tense is used instead of the future." There are two points to be noted here.

10 Introduction
(1) The expression "instead of the future" has no reasonable sense at all. What is meant here is that if the action mentioned in a conditional if-clause refers to the future the present tense of the verb is used. (2) Besides, the rule, thus formulated, is much too strict, and requires some modification. If it is taken literally at its face value, it should mean that in a clause of this type the groups "shall + infinitive" and "will + infinitive" are completely inadmissible. This, however, is rather far from the truth, at least, in so far as the group "will + infinitive" is concerned. This group may, in fact, be found in conditional if-clauses. The verb will apparently has a certain trace of its lexical meaning preserved, but the group nevertheless is an analytical form of the future tense, as will be seen from the following example: Twenty thousand francs for you, Madame, if you'll stop breathing on my neck and go away. (R. WEST) Thus, an absolute prohibition of the use of "will + infinitive" in conditional if-clauses proves to be a misstatement of the facts of the language. With reference to the group "shall + + infinitive" the statement appears to be more true. Indeed it is hard to find examples of such a use, and the rule may be laid down with a very high degree of probability.
Careful observation of the facts of the language and attention to their possible stylistic colouring (compare also p. 354 ff.) will often help to modify some too strict prohibitions and assertions of impossibility to be found in grammarians' statements.