464. The number of possible tenses is very great. For in each of the three times, present, past, and future, an action may be represented as on-going, completed, or beginning; as habitual or isolated; as defined in time or indefinite (aoristic); as determined with reference to the time of the speaker, or as not itself so determined but as relative to some time which is determined; and the past and future times may be near or remote. Thus a scheme of thirty or more tenses might be devised.
But, in the development of forms, which always takes place gradually, no language finds occasion for more than a small part of these. The most obvious distinctions, according to our habits of thought, appear in the following scheme.
|1. Definite||2. Indefinite|
|Present:||a. I am writing.||d. I have written.||g. I write.|
|Past:||b. I was writing.||e. I had written.||h. I wrote.|
|Future:||c. I shall be writing.||f. I shall have written.||i. I shall write.|
Most languages disregard some of these distinctions, and some make other distinctions not here given. The Indo-European parent speech had a present tense to express a. and g., a perfect to express d., an aorist to express h., a future to express c. and i., and an imperfect to express b. The Latin, however, merged the perfect and aorist into a single form (the Perfect scrīpsī), thus losing all distinction of form between d. and h., and probably in a great degree the distinction of meaning. The nature of this confusion may be seen by comparing dīxī, dicāvī, and didicī (all perfects derived from the same root, DIC), with ἔδειξα, Skr. adiksham, δέδειχα, Skr. dideça. Latin also developed two new forms, those for e. (scrīpseram) and f. (scrīpserō), and thus possessed six tenses, as seen in § 154.c.
The lines between these six tenses in Latin are not hard and fast, nor are they precisely the same that we draw in English. Thus in many verbs the form corresponding to I have written (d.) is used for those corresponding to I am writing (a.) and I write (g.) in a slightly different sense, and the form corresponding to I had written (e.) is used in like manner for that corresponding to I was writing (b.). Again, the Latin often uses the form for I shall have written (f.) instead of that for I shall write (i.). Thus, nōvī (I have learned) is used for I know; cōnstiterat (He had taken his position) for He stood; cōgnōverō (I shall have learned) for I shall be aware. In general a writer may take his own point of view.