Mood signifies manner.  Applied to verbs it explains how, in what manner, by what means, under what circumstances, actions are performed.

There are three moods, the indicative or declarative, the imperative or commanding, and the infinitive or unlimited.

The indicative mood declares an action to be done or doing, not done, or not doing.  It is always in the past or present tense; as, David killed Goliath; scholars learn knowledge; I spoke not a word; they sing not.

The imperative mood denotes a command given from the first person to the second, to do or not do an action.  It expresses the wish or desire of the first person to have a certain action performed which depends on the agency of the second.  The command is present, but the action signified by the word is future to the giving of the command.  The second person cannot comply with the will of the first till such will is made known; as, bring me a book; go to the door.

The infinitive mood has no direct personal agent, but is produced as a necessary consequence, growing out of a certain condition of things.  It is always future to such condition; that is, some prior arrangement must be had before such consequences will follow.  It is always future; as, they are collecting a force to besiege the city.  We study grammar to acquire a knowledge of language.  Windows are made to admit light.  The act of besieging the city depends on the previous circumstance, the collection of a force to do it.  Were there no windows, the light would not be admitted to the room.

These distinctions in regard to action must be obvious to every hearer.  You all are aware of the fact that action necessarily implies an actor, as every effect must have an efficient cause; and such action clearly or distinctly indicated, must have such an agent to produce it. 2d.  You are acquainted with the fact that one person can express his will to the second, directing him to do or avoid some thing. 3d.  From an established condition of things, it is easy to deduce a consequence which will follow, in the nature of things, as an unavoidable result of such a combination of power, cause, and means.

With these principles you are all familiar, whether you have studied grammar or not.  They are clearly marked, abundantly simple, and must be obvious to all.  They form the only necessary, because the only real, distinction, in the formation and use of the verb to express action.  Any minor distinctions are only calculated to perplex and embarrass the learner.

But some grammarians have passed these natural barriers, and built to themselves schemes to accord with their own vain fancies.  The remarks of Mr. Murray upon this point are very appropos.  He says: