Want to be known as an eloquent speaker and compelling writer? Use the subjunctive mood more. Use it to express a wish, a demand, a requirement, an exhortation, or a statement contrary to fact--as well as in a number of fixed idioms.
Generally. The subjunctive mood is peculiar in form and function. It is little used except in a few fixed phrases. A verb in the subjunctive mood has no third-person-singular (-s) variation; be is used rather than am, are, and is [if I be honest]; and were is used instead of was [if he were honest].
The present tense may be used to express would-be conditions in the past [truth be told, their objection should have been sustained], and the past tense to express would-be conditions in the present [I would not do that if I were you].
- Be that as it may, the suit has already been filed. (Be that as it may is a fixed phrase in the subjunctive mood.)
- If you be honest you will admit liability for the accident. (The stilted sound of if you be honest reflects the archaic nature of the subjunctive mood. But changing it to if you were honest changes the tone from "you can be honest" to "you are dishonest.")
"That"-clause of need. Use the subjunctive mood in that-clauses of request, demand, or requirement. If a be-verb is required, use be (regardless of person and number) and the past or present participle, regardless of when the action takes place. If no be-word is required, use the present-tense stem alone, regardless of when the action takes place.
- We insist that we be allowed to review the document before it is admitted into evidence. (Be allowed to review is subjunctive, expressing a request.)
- Rule 11 requires that lawyers use good faith in making and responding to discovery requests. (Use is subjunctive, expressing requirement.)
- The retiring judge told about being a first-year law student whose torts professor insisted that he study harder or face certain failure. (Study is present-tense subjunctive, expressing a demand.)
- The foundation requires that a scholarship recipient be enrolled full-time to maintain eligibility. (Be enrolled is subjunctive, expressing a requirement.)
To express a wish. Use the past-tense subjunctive mood with the word were (regardless of person and number) to indicate a wish. Use the past tense to indicate a present-time wish.
- I wish Maria were more certain about her decision. (Were is subjunctive; the indicative verb would be was. The past-tense form attains a present-time meaning in the subjunctive mood.)
- Don't you wish you were a fly on the jury-room wall?
- I wish I were in Dixie.
Exhortations and things contrary to fact. Use the subjunctive mood in clauses starting with if, as if, or as though to express exhortations and things contrary to fact (including suppositions and illusions as well as impossible things).
- If we were to offer $75,000, would you take it?
- Any reasonable official would have known that a choke hold was excessive force, but the officer acted as if immunity would protect him.
- The cross-examination seemed as though it were never going to end. (An illusion: were going to end is subjunctive.)
- Long live rock 'n' roll! (An exhortation: may is understood so the meaning is may rock 'n' roll live long.)
Fixed idioms. Use the subjunctive mood as it occurs in many fixed phrases.
- If I were you . . . .
- I need be . . . .
- So help me God . . . .
Source: The Redbook: A Manual on Legal Style by Bryan A. Garner.