3.  Very often, instead of the simple subjunctive forms, we use auxiliary verbs—­may (past, might) and would or should—­to express the subjunctive idea.  “May” ("might”) is common as an equivalent for the subjunctive mode in clauses denoting a purpose, a wish, a hope, or a fear:  as, “Bring him the book, that he may read to us;” “May he rest in peace;” “I hope you may succeed;” “They were afraid we might lose the way.”  “Would” and “should” are common substitutes for all tenses of the subjunctive:  as, “Walk carefully lest you (stumble) should stumble;” “If he (come) should come, he will find me at home;” “It (were) would be better if he (went) should go alone;” “If my sister had seen this mouse, she (had been) would have been frightened.”  In these sentences either the form in parenthesis or the italicized form is correct, though the latter is more common.

NOTE.—­It does not follow that the verbs “may,” “would,” and “should” always express the subjunctive idea.  In the following sentences, for instance, they express the indicative idea:  “You may (i.e., are permitted to) stay an hour;” “You should (i.e., ought to) be punctual;” “Edith would not (i.e., was unwilling to) come.”  In such sentences “may,” “should,” and “would” make simple statements of fact.

USES of the SUBJUNCTIVE.—­The indicative form is used in expressing a fact or what is assumed to be a fact:  as “He thinks he is ill;” the subjunctive form indicates some uncertainty or doubt in the speaker’s mind:  as, “Whether it rain or not, I will go.”

The subjunctive idea occurs most frequently, perhaps, in conditional sentences.  A conditional sentence is one that contains a condition or supposition.  A supposition may refer to present, past, or future time.  If it refers to present or past time, it may be viewed by the speaker as true, untrue, or as a mere supposition with nothing implied as to its truth; if it refers to the future, it may be viewed as either likely or unlikely.  A supposition which is assumed to be true, or which is made without any hint as to its correctness, is expressed by the indicative.  A supposition which is viewed by the speaker as untrue or unlikely is expressed by the subjunctive or a periphrase[87] for the subjunctive.  When the character of the supposition makes the conclusion untrue or unlikely, the conclusion also is expressed by the subjunctive or a periphrase[87] for the subjunctive.  The use of tenses is peculiar, as will be seen from the following table of a few common forms of conditional sentences.  The tenses should be carefully noted:—­

PRESENT:  If it rains (is raining) now, I am sorry. Present indicative:  A simple supposition without any hint as to its correctness.

    If it rained (were raining), I should be sorry.
    Past subjunctive, both clauses:  The speaker implies that it is
    not raining.