i saw Tom cross the street .

[liuchunsheng123456]

" i saw Tom cross the street " when this sentence changes into passive voice , it becomes " Tom was seen to cross the street". Could you tell me the reason why the "TO" add here.
In this sentence "Tom was seen to cross the street ", the action "cross"is still be emphasized as a completion ? in my opion ,it should be " Tom was seen to having cross the street."

[Polux]

I'm really but really not sure of what I am about to say but...

I think it should more be :
Tom was seen crossing the street.

Because it happened in a precise time in the past and because at that precise time in the past he was presently doing something. He was somewhere near both side of the road but not at his endpoints.

It's not an habit... we don't have any clue... he just... crossing the street ?

That is what I thought.
Correct me if wrong :)

Polux

[Dr. Jamshid Ibrahim]

" i saw Tom cross the street " when this sentence changes into passive voice , it becomes " Tom was seen to cross the street". Could you tell me the reason why the "TO" add here.
In this sentence "Tom was seen to cross the street ", the action "cross"is still be emphasized as a completion ? in my opion ,it should be " Tom was seen to having cross the street."

This is infinitive after verbs of sensation like: hear, see, which shows: I saw the complete action: I saw him repair the car, in comparison with present participle which might refer either to a complete or an incomplete action: I saw him repairing the car.
In the passive after verbs of sensation like “see” the full infinitive is used:
He was heard to say that his wife left him.

[liuchunsheng123456]

　　Ｔhe word "to " ,in my opinon , often express the meaning " will do something " ,but now it express the meaning " have completed ", i think it should be "Tom was seen to having cross the street " is more natural than " Tom was seen to cross the street ". Was there any changes in this sentence patter ? Did "Tom was seen to cross the street " change from " Tom was seen to cross the street ?" It just my guess, i am very interested in the origin of English .
Could someone give me some advice?
Thank you in advance .

[Dr. Jamshid Ibrahim]

You are confusing two functions of the word „To“
1. It can be a preposition followed by gerunds/nouns:
I look forward to meeting her.
2. Part of the infinitive
I want to go

l already mentioned it is part of the infinitive (full infinitive) here. Where is your problem?

[liuchunsheng123456]

thank you very much .;)