The category of mood denotes modality or the relation of the contents of the utterance to reality as viewed by the speaker. Modality is a wide notion which characterises every sentence.
Means of expressing modality: lexical (modal verbs), lexico-grammatical (modal words), morphological (mood), syntactic (structure of the sentence), phonetic (intonation). Linguists distinguish between objective modality (expressed by mood-forms) and subjective modality (expressed by lexical and lexico-grammatical means). The category of mood is proper to finit forms of the verb. It is closely connected with the syntactic function of the predicate. The category is revealed both in the opposition of forms and syntactic structures. So the category of Mood has a strong syntactic significance.
Linguists distinguish from 2 to 16 moods in Modem English. The reasons are as follows:
1. The category of mood is in the state of development. Some forms have a limited sphere of use (he, be), new forms are coming into the system (let).
2. There is no direct correspondence of meaning and form. There are no special forms for expressing unreal actions (with the exception of the forms he be, he were). The same forms are used to express facte and non-facts: should/would do, did. They are treated either as homonymous or as polysemantic.
3. It is difficult to distinguish between mood auxiliaries and modal verbs: may, let.
All the scholars recognize the opposition of 2 moods: indicative and imperative.
Indicalive is represented by a system of categories, (tense, order, aspect, voice, etc.). It is a fact-mood or a direct mood. Imperative is represented by one form, which is used in sentences with implied subject.
G.N.Vorontsova recognizes the analytical form of the imperative, expressed by let+ Infinitive.
Problematic and unreal actions are expressed by 4 sets of forms. The form (he) be/come/take, expressing a problematic action, is the only form which differs from the forms of the indicative. There is one more form of the verb to be, different from the forms of the indicative: (he) were. But this difference disappears in all other verbs, and besides, the form (he) was is now being replaced by the form (he) was. The combinations (he) should be, (he) should have been do not differ from modal phrases.
Forms expressing unreal actions are the same as the forms of the past indicative. These forms are often treated as polysemantic, i.e. forms of the indicative, which express unreal actions in certain syntactic structures (R.Quirk, L.S.Barkhudarov). Forms of the past indicative denote actions, not connected with the moment of speaking, not “relevant” for the speaker, “not real” now. That is why they may be used to denote unreality. In this case subjunctive will be represented by 2 forms of the verb to be: (he) be, (he) were and 1 form of other verbs: (he) do, come, go.
A.I.Smimitsky: these forms are homonymic, denoting real and unreal actions: they were ... - real, past; if they were ... - unreal, non-past. Subjunctive is represented by 4 sets of forms. In this system of 4 sets of forms, denoting different degree of unreality, there is no direct correspondence of meaning and form:
a) one meaning - different forms: I suggest you do (should do) it.
b) one form - different meanings: I suggest you should do it. In your place I should do it.
The number of oblique moods will depend on the basic principle for distinguishing between them: a) meaning; b) form; c) both meaning and form,
a) B.A.llyish treats these 4 sets of forms as forms of one mood - subjunctive. The difference of form and particular meanings is disregarded: only the common component of meaning (unreality) is taken into account.
b) A.I.Smirnitsky takes into account the difference in form and recognizes 4 oblique moods: Subjunctive I (he be), Suppositional (he should be), Subjunctive II (he were), Conditional (should/would be).
c) The system of forms, expressing different degrees of unreality, will be subdivided into 2 parts:
1. Forms, denoting problematic actions (he be, should be) may be treated as forms of one mood (Subjunctive I), the analytical form ousting the synthetic form in British English.
2. Forms, denoting unreal actions (were, should/would be) are treated as different moods, expressing independent and dependent unreality, or unreal condition and unreal consequence. But their modal meaning is the same and were - should be are not opposed as moods. This opposition reveals the category, which also exists in the system of the indicative mood.
So the wide divergence of views on the number of oblique moods can be accounted for:
a) by different approaches to the problem of polysemy/homonymy;
b) by the absence of mutual relation between meaning and form.
In the system of the indicative mood time may be denoted absolutely (tense) and relatively (order, posteriority). In the system of the subjunctive mood time may be denoted relatively (order, prospect). Perfect forms denote priority, non-perfect forms - simultaneousness with regard to other actions. The category of order may acquire the meaning of the category of tense.