English verbs have three moods: indicative, imperative, and subjunctive. The indicative mood (the most common) is used to state a fact or an opinion or to ask a question (I will go to sleep now. Do you want to go to sleep now?) The imperative mood expresses a command, gives a direction, or makes a request (Got to sleep now! Please, go to sleep now); it omits the subject of the sentence – the implied you. The troublesome and complicated subjunctive mood (discussed below) expresses wishes, suggestions, and other attitudes, using I were and other distinctive verb forms (If I were you, I would go to sleep now.)
Forming the Subjunctive Mood
The present subjunctive uses the base form of the verb, regardless of the subject (The professor recommended that I study harder). The past subjunctive has the same form as the past tense of the verb, The verb to be, however, takes the form were regardless of the number and person of the subject (I wish I were Emperor of the World; If I were rich, I could retire).
When the Subjuctive Is Used
> Use the past subjunctive in contrary-to-fact clauses that state imaginary or hypothetical conditions (often called conditional statements). Such statements usually begin with if (or unless) or follow the verb wish. For present contrary-to-fact clauses, use the verb's past tense; if the verb is to be, use were.
If I were rich and had a yacht, I would cruise all over the world.
I wish I were wise, rich, and beautiful, but I am stupid, poor, and ugly.
For past contrary-to-fact clauses, use the verb's past perfect form (had + past participle).
If the firm had been better managed, it would not have gone bankrupt.
I would have gotten away with it if I had kept my mouth shut.
> Use the present subjunctive in statements that express a suggestion, requirement, or request. Such statements use verbs such as ask, insist, urge, require, demand, recommend, and suggest. These verbs often precede a subordinate clause beginning with that, with the clause containing the substance of the request, requirement, or suggestion. (For all subjects, the verb used is the base form.)
The doctor insisted that she walk at least a mile a day.
The professor requires that each student write six essays in the course.
John's father demanded that he apologize for burning down the neighbors' house.
Sources: LB Brief by Jane E. Aaron (Longman: 2002); The Brief Holt Handbook (3rd ed.) by Laurie G. Kirszner and Stephen R. Mandell (Harcourt: 2001).