kare ni ha isiki ga arimasu.

には is に + は.

Here, に marks the person or thing that has something in a more formal or abstract pattern:

• N に は X がある
• literally: As for N, there is X

So 彼には意識があります is structurally like As for him, consciousness exists.

The は adds topic or contrast. It often gives a nuance like:

• as for him
• he, at least
• in his case

If you said 彼は意識があります, it would sound unnatural in standard Japanese.

In this pattern, に marks the location/existence target for what is possessed.

Japanese often expresses to have as something exists with/for someone rather than using a direct verb meaning have.

So:

• 彼に意識がある
• literally: Consciousness exists in/with him

This is why に is used instead of something like a direct object marker.

が marks the thing that exists: 意識.

With ある / いる, the thing that exists is usually marked by が:

• 本がある = there is a book
• 人がいる = there is a person
• 意識がある = consciousness is present

So in 彼には意識があります, the sentence is built around 意識がある and 彼には sets the frame: as for him.

あります is used because 意識 is not a living person or animal. It is treated as an abstract thing/state.

Very roughly:

• いる → for animate beings
• ある → for objects, abstract things, states, events

Since 意識 means consciousness / awareness, Japanese uses ある.

The は in には often adds a topic or contrast nuance.

So 彼には意識があります can sound like:

• As for him, he is conscious
• He does have consciousness
• At least he is conscious

Depending on context, this may contrast him with someone else:

• 彼女には意識がないが、彼には意識がある
• She is unconscious, but he is conscious

Without context, it may simply mark him as the topic.

It is grammatical and natural, especially in formal, medical, or report-like contexts.

Common expressions include:

• 意識がある = to be conscious
• 意識がない = to be unconscious

In everyday conversation, you might also hear:

• 彼は意識がある
• 彼は意識がない

This version uses 彼は as the topic and leaves 意識がある as the predicate.
But when you specifically want the possessor pattern, 彼には意識があります is also very natural, especially when emphasizing him.

彼には意識があります is the more natural form if you are using the X に Y がある pattern.

Why? Because 意識がある is being treated like consciousness exists in/for him, and that pattern normally uses に.

彼は意識があります sounds awkward because 彼 is marked only as a topic, but the sentence still feels like it wants the possessor marker に.

A better comparison is:

• 彼には意識があります
• 彼は意識がある

Both can mean roughly the same thing, but their structure is different:

• 彼には意識があります → possession/existence framing
• 彼は意識がある → topic + predicate

Yes. In normal Japanese writing, spaces are usually not used.

The standard written form is:

彼には意識があります。

The spaced version is just for learners so they can see the parts more easily.

あります is the polite form of ある.

So:

• 彼には意識がある。 → plain style
• 彼には意識があります。 → polite style

The meaning is the same. The difference is just level of politeness and formality.

意識 has a few related meanings depending on context:

• consciousness in the medical sense
• awareness
• conscious intention / attention

In this sentence, because of 意識がある, it most naturally means being conscious rather than unconscious.

For example:

• 意識があります = is conscious
• 環境を意識する = be conscious of / aware of the environment

So the exact meaning comes from the expression it appears in.

Yes. That is one of the common effects of は, especially in には.

For example:

• 彼女には意識がありませんが、彼には意識があります。
• She is unconscious, but he is conscious.

In that kind of context, には strongly suggests contrast.
Even without an explicit comparison, listeners may sometimes feel a slight as for him... nuance.

A very useful pattern is:

• A には B がある
• As for A, there is B
• often translated as A has B

Examples:

• 私には時間があります。 = I have time.
• 彼には才能があります。 = He has talent.
• 彼には意識があります。 = He is conscious / He has consciousness.

So this sentence is a good example of how Japanese often expresses having by using ある plus particles rather than a separate verb like English have.