Very often verbs are described as if they are either stative or dynamic. Stative verbs (also called state verbs) are seen as those which describe something unchanging :
I know that!
I remember her well.
I love chocolate!
He's from London
These states can only be expressed using simple aspect - the progressive is impossible in any of the above examples.
On the other hand, dynamic verbs (also called event verbs) are seen as referring to an occurrence with a distinct beginning and end. The distinction made is that dynamic verbs can be used with either simple or progressive aspect :
Anne held up her hand / Ann was holding up her hand.
It rained heavily that day / It was raining heavily that day.
However, looked at more closely, the distinction doesn't hold up. Verb forms express meanings and the form chosen will depend on what meaning the speaker wants to express. Almost any verb can be used statively or dynamically. If it's used statively, then the event is seen as a permanent fact/state and simple aspect will be used; if it's used dynamically then the event is seen as an on-going but temporary event and progressive aspect will be chosen. For example, compare :
- I agree and We were agreeing last night how much better it was.
- I remember her well and Today we are remembering those who died in...
- I love chocolate! and David's in France for three months and he's loving every moment of it.
- He's from London and He's being stupid.
So it depends on the speaker's perception of the event : if you perceive something as a permanent fact/state then you'll use simple aspect; if you perceive it as an on-going but temporary event/action, then you'll choose the progressive°. But either can be used with most verbs. Some of the very few exceptions would seem to include : consist, contain, depend, fit and know - none of which occur in the Brown or BNC corpora in the continuous form.
* My favourite example of this was the way, after I'd been living in Italy for about ten years, I would say I live in Italy - having no intentions of moving and therefore seeing the situation as permanent. Yet for a long time, my mother would continue to tell her friends Sue is living in Italy, clearly hoping and wanting to believe that it was temporary - despite all evidence to the contrary.