The ordinary Greek grammar gives a complete paradigm of the verb, without suggesting that the double or treble forms of Perfects, Aorists, etc. are hardly ever contemporaneous. It distinguishes Moods and Tenses, without observing how much of the nature of one passes into the other. It makes three Voices, Active, Passive, and Middle, but takes no notice of the precarious existence and uncertain character of the last of the three. Language is a thing of degrees and relations and associations and exceptions: grammar ties it up in fixed rules.