I know him. He is known to me

Question

I am really dejected about the "Passive sentence" of this "Active sentence" = I know him.

One of my friends told me that "He is known to me" is not a passive sentence. He said that it is like this "He is industrious, or he is intelligent". "KNOWN" IS ADJECTIVE HERE.

I am really confused about this sentence. Even we know that "in passive" the word "Know" is followed by preposition "To". Is it not a passive sentence?

My friend's explanation is given below.

I know him.

This sentence cannot be changed into passive voice. The verb (know) is a stative verb here. A knows B. It's just a statement, no action is taking place. Similar sentence:
☞I am James.
This is also a statement. (No action is taking place, it's just my name.) So, this sentence cannot be changed into passive voice. If you think "He is known to me." is in passive form, then you need to know that "known" is an adjective here.

It's not v3. He is known (adjective) to me. So, this is not the passive form. Similar example: He is worried (adjective) about him. The right answer is: The given sentence cannot be changed into passive voice.

He is known to me.

Answer 1

As commented above, the two sentences don't have the same meaning. In order to understand what the passive voice is, you need to understand the followings.

1. There should be an agent (that performs an action) and patient (that receives an action). The definition of patient is as follows:

the semantic role of a noun phrase denoting something that is affected or acted upon by the action of a verb.

In the passive voice, the agent is almost always placed after the preposition by. The reason the preposition to is used in your example is "known" is not a past participle, but an adjective meaning:

recognized, familiar, or within the scope of knowledge.

In "I know him", "I" is an agent and "him" is a patient (object). However, "He is known to me", "He" is not an patient in a sense that it doesn't receive any action. "He" is just a subject which is described by the adjective "known". If you replace "known" with "familiar", it would be easier to understand.

He is familiar to me.

It is not a passive voice sentence.

2. Not all the past participles are used in the passive voice. Sometimes they function as an adjective. There is no hard-and-fast rule, but for example,

He was surprised at the news.

This sentence is not in the passive voice. "Surprised" is just an adjective meaning feeling or showing surprise. "At the news" is a prepositional phrase that complements the adjective.

The news surprised him.

is an active voice. The passive voice of the above sentence should be

He was surprised by the news. (He is the patient, the news is the agent)

The below sentence is in the passive voice of "A baseball broke the window".

The window was broken by a baseball.

However, the below sentence is not in the passive voice. There is no agent.

The window was broken and a strong wind came through it (the broken window).

3. To know is classified as a stative verb rather than a dynamic (action) verb. The main characteristics of the stative verb are:

(1) you don't make a progressive sentence with it (there are some exceptions),

(2) Constructing a passive voice of the stative verbs don't work very well and the passive voice sentences don't sound natural.

?He is known by me (I know him). ?A car is had by me (I have a car). ?He is believed by me (I believe him).

This link has a list of stative verbs. Learning what they are and how they typically work is very important.

Conclusion: "He is known to me" is not in the passive voice. "Known" is an adjective, not a past participle. If you contrast your example with "He is well-known to me", it becomes clearer. It is not the passive voice of "I know him well".

Answer 2

He is known to me.

Known here is a past participle functioning as an adjective. It is not a passive construction

What your sentence means is

To me, he is known.

Compare this with an adjective:

He is funny to me.

equals

To me, he is funny.

Sometimes it is very difficult, if not impossible, to determine whether a given sentence is a passive construction or not.

See "I am surprised": passive voice or adjective?

The classic case is

The window was broken.

Is broken an adjective or a passive verb form? It could be either, And without context it's impossible to say. Adding an agent clarifies that it is a passive construction:

The window was broken by me.

Also consider:

The store is closed every night at eight.

Closed could be an adjective or a part of a passive verb construction.

Adjective:

The store is not open but closed every night at eight when I walk past it.

Passive:

The store is closed every night at eight by me. This involves taking out the trash and locking all the store's doors before I go home.

Some verbs have both an active and stative sense. Known is one of these.

I know this song.

Could a passive be formed:

? This song is known by me.

To a native speaker, that sounds pretty weird.

You found a sentence that uses know in a passive construction:

"The Earth was known by Galileo to be a sphere".

(Active equivalent: Galileo knew the Earth to be a sphere".)

I worry him.

is a perfectly good active sentence, with a direct object; but still it makes a questionable passive:

?? He is worried by me.

sounds very strange.

Last, know has an old-fashioned meaning, equivalent to lie down together (and have sex).

Adam knew Eve and she conceived and bore him a son.

can be changed into a passive:

Eve was known by Adam, and she conceived and bore him a son.

This is what is called to know someone 'in the biblical sense, because this use of know was made famous by the King James translation of the Holy Bible.

Answer 3

1. I know him ... know is the present tense of the verb

2. He is known ... known is the passive participle of the verb

3. He is known to me

4. He is known by me

We construct a sentence in the passive voice using a passive participle- in this case known. A passive participle functions as an adjective in a sentence.

Sentences 2 to 4 are all passive voice. In sentences 3 and 4 we link additional information to the sentence using a preposition to or by, but it does not change the fact that the main part of the sentence is passive voice.

know is a stative verb in this context, and it is true that there are some stative verbs that you cannot use for passive voice sentences. Examples are: belong, have (own), lack, resemble, suit. This article explains about verbs which cannot be used in passive voice, and clearly states that know can be used in passive voice, quoting this example:

Nothing is known about the thief

You are therefore right that this is a passive voice sentence.

Your friend is partially right on two counts: known is a kind of adjective, and know is a stative verb, but is wrong about the sentence not being passive voice.