OBS. 3.—­The Potential mood is so called because the leading idea expressed by it, is that of the power of performing some action.  This mood is known by the signs may, can, must, might, could, would, and should.  Some of these auxiliaries convey other ideas than that of power in the agent; but there is no occasion to explain them severally here.  The potential mood, like the indicative, may be used in asking a question; as, “Must I budge? must I observe you? must I stand and crouch under your testy humour?”—­Shakspeare.  No question can be asked in any other mood than these two.  By some grammarians, the potential mood has been included in the subjunctive, because its meaning is often expressed in Latin by what in that language is called the subjunctive.  By others, it has been entirely rejected, because all its tenses are compound, and it has been thought the words could as well be parsed separately.  Neither of these opinions is sufficiently prevalent, or sufficiently plausible, to deserve a laboured refutation.  On the other hand, James White, in his Essay on the English Verb, (London, 1761,) divided this mood into the following five:  “the Elective,” denoted by may or might; “the Potential,” by can or could; “the Determinative” by would; “the Obligative,” by should; and “the Compulsive,” by must.  Such a distribution is needlessly minute.  Most of these can as well be spared as those other “moods, Interrogative, Optative, Promissive, Hortative, Precative, &c.”, which Murray mentions only to reject.  See his Octavo Gram., p. 68.

OBS. 4.—­The Subjunctive mood is so called because it is always subjoined to an other verb.  It usually denotes some doubtful contingency, or some supposition contrary to fact.  The manner of its dependence is commonly denoted by one of the following conjunctions; if, that, though, lest, unless.  The indicative and potential moods, in all their tenses, may be used in the same dependent manner, to express any positive or potential condition; but this seems not to be a sufficient reason for considering them as parts of the subjunctive mood.  In short, the idea of a “subjunctive mood in the indicative form,” (which is adopted by Chandler, Frazee, Fisk, S. S. Greene, Comly, Ingersoll, R. C. Smith, Sanborn, Mack, Butler, Hart, Weld, Pinneo, and others,) is utterly inconsistent with any just notion of what a mood is; and the suggestion, which we frequently meet with, that the regular indicative or potential mood may be thrown into the subjunctive by merely prefixing a conjunction, is something worse than nonsense.  Indeed, no mood can ever be made a part of an other, without the grossest confusion and absurdity.  Yet, strange as it is, some celebrated authors, misled by an if, have tangled together three of them, producing such a snarl of tenses as never yet can have been understood without being thought ridiculous.  See Murray’s Grammar, and others that agree with his late editions.