There are some verbs which cannot be used in the progressive or continuous tenses. We can say "I am reading a book" when we wish to express that the action of reading is in progress. However, we cannot say "I am seeing somebody who is trying to hide" because the verb "see" indicates an involuntary action: if you are not blind, you see; you are able to see something or not. So you need to say "I am looking at somebody who is trying to hide". You see that person and you are looking at that person.
The general rule is that verbs which cannot be use in progressive or continuous tenses are those related to mental processes, emotional states, possession, sense perception (the senses, which are involuntary actions), and then some other, difficult to classify. Here are some examples:
I want to get a new pair of jeans.
I believe/think/feel/imagine you could be wrong.
I didn't realize what you meant
I understand your point, but I don't agree.
I forgot to bring the keys!
Yes, I remember.
I doubt it.
I mean, I would like to see you more often.
I love you
I hate it - I hate going out at weekends!
Do you mind if I smoke?
They don't care
I appreciate (Thanks!)
I didn't like the movie
I have (got) a brother
Have you got a house?
Do you own a house?
This belongs to me
What does that taste like?
It smells of burning
I can't hear!
Move! I can't see!
It seems we're getting nowhere!
I am a student
I owe you some money, remember?
It includes the meals
It costs 2,000 euros!
But of course, the story is not that simple (Surprise, surprise...)
There are some verbs which change their meaning depending on whether they are used in the progressive or non-progressive tenses! Consider the following examples:
State of Existence
Action in Progress
|I think he's really nice
We have a small flat
This meal tastes delicious!
Your perfume smells great!
I see it!
Velvet feels so soft!
You look tired
You appear to be sad
The baby weighs ... kg
I am hungry
|I'm thinking of buying a new computer
We're having some difficulties at the moment
The cook is tasting the broth
The girl is smelling the flowers
We are seeing the doctor at six
We were feeling our way in the dark!
They are looking at the pictures
Vanessa Redgrave is appearing at the Royal Theatre
The greengroce is weighing the apples
You're being a bugger! So bugger off!