Did you ever wonder how both Simple and Continuous tenses could be used in the same contexts and with the same markers and why? Like this:

"Present Indefinite (Simple Present) is used for:
2. Actions that are repeated regularly in present (my translation - RC).
He always comes to school on time.


6. Continuous group tenses also are used to emphasize a too frequent excessive repetition of some action... In these instances the markers like always or constantly are used (my translation - RC):
You are always losing your key!
You are constantly grumbling!

http://www.englishlearner.ru/tags/present+continuous /

Seems to be another "ah-use-whichever-you-want" instance, which does not add respect to English grammar, of course. But what is the reason for the duality of these repetitive, habitual or traditional contexts that undermine already fragile grammar card house?

It's aspects. Yes, again.

With the course of time the English people started to notice that other nations regarded verbs dually. The smartest English people, especially those familiar with Aristotle's works, understood that the duality implied the "process vs. event" opposition. They found it logical and wanted to have this opposition in their language too. Without introducing the category of aspect, though. Just by means of the available tools. One of them were Continuous tenses. The reason of substituting Simple tenses with Contiunous ones in the above mentioned contexts is in that Simple tenses did not allow to tell processes from events (which is, imperfect aspect from perfect aspect). While with Continuous tenses this problem seemed to be eliminated:

She constantly grumbled. - unclear aspect
She was constantly grumbling - clear imperfect aspect

For this same reason you may encounter the use of Perfect tenses outside of their "typical" contexts and with no "traditional" markers in sight:

"One September night a family had gathered around their hearth and piled it high with the driftwood of mountain streams, the dry cones of the pine and the splintered ruins of great trees that come crashing down the precipice. Up the chimney roared the fire..."
"The Ambitious Guest" - Nathaniel Hawthorne

The reason Hawthorne used a perfect tense was his subconscious aversion for simple tenses, that do not tell the aspects. Read the books attentively, and you will find more instances of that kind.

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