the second, not to can.”—­Ld.  Bacon.  “That a verb which signifies knowledge, may also signify power, appears from these examples:  Je ne saurois, I should not know how, (i. e. could not.) [Greek:  Asphalisasthe hos oidate], Strengthen it as you know how, (i. e. as you can.) Nescio mentiri, I know not how to (i.e. I cannot) lie.”—­W.  Allen’s Gram., p. 71. Shall, Saxon sceal, originally signified to owe; for which reason should literally means ought.  In the following example from Chaucer, shall is a principal verb, with its original meaning: 

   “For, by the faith I shall to God, I wene,
    Was neuer straungir none in hir degre.”—­W.  Allen’s Gram., p. 64.

OBS. 15.—­Do and did are auxiliary only to the present infinitive, or the radical verb; as, do throw, did throw:  thus the mood of do throw or to throw is marked by do or to. Be, in all its parts, is auxiliary to either of the simple participles; as, to be throwing, to be thrown; I am throwing, I am thrown:  and so, through the whole conjugation. Have and had, in their literal use, are auxiliary to the perfect participle only; as, have thrown, had thrown.  Have is from the Saxon habban, to possess; and, from the nature of the perfect participle, the tenses thus formed, suggest in general a completion of the action.  The French idiom is similar to this:  as, J’ai vu, I have seen. Shall and should, will and would, may and might, can and could, must, and also need, (if we call the last a helping verb,) are severally auxiliary to both forms of the infinitive, and to these only:  as, shall throw, shall have thrown; should throw, should have thrown; and so of all the rest.

OBS. 16.—­The form of the indicative pluperfect is sometimes used in lieu of the potential pluperfect; as, “If all the world could have seen it, the wo had been universal.”—­Shakspeare.  That is,—­“would have been universal.”  “I had been drowned, but that the shore was shelvy and shallow.”—­Id. That is,—­“I should have been drowned.”  This mode of expression may be referred to the figure enallage, in which one word or one modification is used for an other.  Similar to this is the use of were for would be:  “It were injustice to deny the execution of the law to any individual;” that is, “it would be injustice.”—­Murray’s Grammar, p. 89.  In some instances, were and had been seem to have the same import; as, “Good were it for that man if he had never been born.”—­Mark, xiv, 21.  “It had been good for that man if he had not been born.”—­Matt., xxvi, 24.  In prose, all these licenses are needless, if not absolutely improper.  In poetry, their brevity may commend them to preference; but to this style, I think, they ought to be confined:  as,