On verbs: tense and aspect

Remember my table of tenses? Well, apparently it is wrong, at least according to David Crystal. David Crystal says there is NO FUTURE TENSE. Rather, English expresses future time by a variety of other means, such as using the words "will" or "shall".

It makes sense. Because when we write "I ran", "I run", and "I will run", "ran" and "run" signal tense. On other hand, with the verb phrase "will run", "will" is actually a modal verb without any tense markers. Semantically, it carries the meaning of the future, but not it does not signal tense.

Also, it is imprecise to say that verbs like "running" and "have run" are the "progressive tense" and "perfect tense" respectively. This is because the -ing form of the verb does not have anything to do when it happened, whether it is in the present or the past. Rather, it has to do with aspect, which is concerned about duration: is an action continuing or completed? There are two aspects in English: the progressive aspect (-ing) and the perfective aspect (have).

Note that the word "have" must always be used with the perfective aspect. In the sentence "I have eaten", the perfective-ness of the verb is not determined by the -en form of eaten, but by the word "have". Therefore the sentence "Apples were eaten" is not of the perfective aspect. "Apples were eaten" is in the passive voice.