Who is a kāfir?

Part 1

Apart from the fact that it is Allah (swt) who guides people and Who is the final Judge on the Day of Judgement; what is of concern here is which people can certainly be deemed to be kāfir or disbelievers and who cannot.

That said you only know a person being kāfir by his attitude towards Islam. If he is an active enemy, he is a kāfir. Otherwise, you cannot ascertain it, because it is only God who knows what is in the hearts.
For an in-depth treatment of this issue see ”Who Are The Disbelievers?”^[n1]
”Some of The Main Arguments From Sh. Hamza Yusuf’s Exposition”.

A kāfir is someone who directs his hostile stance against Islam or the Muslims, either with his hand or with his tongue or his pen. He is a kāfir, whether he belongs to any religion or not.

The definition is from the Qur’an, it refers to those who claim that they belong to the people of the Book, but who do not respect Islam or Muslims. In the Qur’an: Those who drive you from your home (Sura 22-40), and those who are fighting against your religion, these people will be seen as kuffār. Those who respect Islam and Muslims and do not fight them, they should be respected equally.

Some people do not agree with something about Islam, if they express their disapproval in a rational, respectful manner, it can be discussed and explained and no harm is involved.

For those who do not follow the Prophet ( sallAllahu `aleihi wa sallam ), or have a ”flawed” faith (`aqīdah), the Qur’an does not call kāfir [ - except if they plainly and openly associate partners to God], for they belong to people of the Book. Then they have their rights, they should be able to practice their religion, their possessions and also their honour will have to be respected, and their women can be married, all of that makes the people of the Book not to be considered kāfir. [Then finally Allah shall judge.]

They are not perceived as kāfir because they have rights with the Qur’an, but once someone takes up arms, or the (evil) word or the (lying) pen against Islam and the Muslims, he will lose these rights.

Kāfir: the covering over (hiding, detracting from) the truth, ie. they know that it is the truth, but they do not want to admit it. They are those who have been told the truth but deny it, so they are called Kāfir (Sura 2-6).

Kāfir can also mean ‘godless’ (Sura 4-151), it depends on the context. The critical limit is his (or her) position towards Islam, either it is a positive attitude or it is a negative attitude.

It follows that if a non-Muslim treats Muslims in a normal and proper manner, he should not be considered as Kāfir, also because it can not be said that he has got correct knowledge about Islam, while he is exposed to the anti-Islam propaganda in the West.

But Allah knows most and best!

Part 2

Are All Non-Muslims Deemed "Kāfir"?

The term “kāfir” refers to someone who is not Muslim—someone who does not believe in the guidance the Prophet (peace and blessings be upon him) came with. There are different types of non-Muslims:

(1) Those who merely do not believe;
(2) Those who reject belief;
(3) Those who dislike belief and believers;
(4) Those who actively oppose and fight belief and believers.
• The verses about enmity to disbelievers refer to this last category.

The Term “Kāfir” as a Derogatory Term

The believer is commanded by Allah and the Messenger (peace and blessings be upon him) to be true, upright, and dignified in speech. Allah Most High says, { Believers, be mindful of Allah and speak only words that are upright. } (Qur’an, 33.70) And to, { Say only good to people. } (Qur’an, 2.83)

The Messenger of Allah ﷺ (peace and blessings be upon him) said, “Whoever believes in Allah and the Last Day should say the good or remain silent.” (Bukhari and Muslim)

Thus, the legal scholars of Islam mention that it is sinful to use terms like “kāfir”^[2] in derogatory or insulting or hurtful ways. (Fatawa Hindiyya)
One must also be careful, spiritually, of the sins of looking down on others, pride, self-consequence, conceit, and similar.

The Fate of Non-Muslims?

Non-Muslims is held responsible for disbelief if the message of guidance reaches them and they reject it.

We do not delve into the specific fate of individuals, whether believers or disbelievers—as their affair is with their Merciful and Just Lord, Allah Most High.

And Allah is the Giver of Success and Facilitation.

Sh Faraz Rabbani (seekershub.org)