I was thrown for a loop when I found out that, in addition to describing events that are happening currently, the ている-form could also be used as past tense:
I have not eaten yet.
I now have come up with an idea that might be able to satisfyingly explain the fact that one verb form can be used for two different tenses. It all comes down to one attribute of the て-form: The verb in the て-form does not show any tense of its own. Instead, its tense seems to be inferred by other verbs and context.
So, what if it is not one and the same ている-form that is being used for past and present, but actually two forms that differ in the hidden tense of the verb in the て-form and thus only appear to be the same?
The verb 食べる in the example above, then, would actually be past tense, which is however not visible because of the て-form superficially overwriting the tense of the verb.
In conclusion: My theory states that when the ている-form is used to describe current events happening in the present, the verb in the て-form is in its present tense. Accordingly, when the ている-form is used to describe events of the past, the verb in the て-form is in its past tense. It's just that this is not visible because the て-form does not allow for a display of tense.
Now, to my actual question: Does this way of trying to explain these circumstances hold any water? Are there any flaws with it that I have overlooked? Feedback would be greatly appreciated!