Are people guilty for not being able to comprehend the evidences ands proofs of Islam; for example, a muslim who is not able to comprehend a verse? And when is a person declared a disbeliever? How much evidence must be shown to a person to establish proof against them? And what if they claim that they do not comprehend ?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

It is proven in the Quran and the Sunnah that a person is not held accountable for that which he is not able to do. Allaah says (what means): {And We charge no soul except [with that within] its capacity, and with Us is a record which speaks with truth; and they will not be wronged.} [Quran 23:62] 

Also, when Allaah revealed the verse that reads {Our Lord, and burden us not with that which we have no ability to bear.} [Quran 2:286] The Prophet said that Allaah said in response to this, “Yes (I have done so).” And another narration reads, “Indeed, I have done so.”

If a Muslim is unable to understand a verse from the Quran, then Allaah will not hold him accountable for that.

As regards when a Muslim is judged to be a disbeliever, then it should first be mentioned that one should refer to the scholars who are well-grounded in religion, and it is not for everyone to declare someone a disbeliever just because he saw him do an act that takes a person out of the fold of Islam.

The scholars do not judge a Muslim to be a disbeliever except if two conditions are met:

Firstly, the act that the person has done is an act that takes him out of the fold of Islam.

Secondly, he does not have an excuse, such as ignorance, or misinterpretation, or coercion; so if he is ignorant (of the ruling of such an act) misinterprets (the matter), or is coerced, then they do not judge him as a disbeliever. The ignorant person should be made aware and the evidence should be established against him.

The scholars differentiate between acts and statements that do not have any other probability except disbelief and those that are probable to involve disbelief and other than it; and they also differentiate between the one likely to have an excuse due to ignorance or misinterpretation or other impediments for declaring someone as a disbeliever and the one that is not.

Besides, there is no given amount of evidence for establishing the evidence, as it is possible to establish the evidence against one person with only one piece of evidence and the evidence may be established with several pieces of evidence if the person does not understand the single proof.

If a person does not understand the evidence, then he is not judged to be a non-Muslim. According to the scholars, understanding the evidence is of two kinds. Shaykh Saalih Aal Ash-Shaykh explains this when explaining Al-‘Aqeedah At-Taahawiyyah, as he says:

"Understanding the evidence is of two kinds:

1) Understanding the evidence means understanding the meanings of the evidence; this is a must, so it is not enough to establish evidence against a non-Arab who does not understand the Arabic language if a verse is recited to him in Arabic while he does not understand its meaning and then say that the Quran has reached him, and Allaah says (what means): {that I may warn you thereby and whomever it reaches.} [Quran 6:19] This is not sufficient; as the evidence must be in a language that the one against whom the evidence is established understands; Allaah says (what means): {And We did not send any messenger except [speaking] in the language of his people to state clearly for them.} [Quran 14:4]

2) The second meaning for understanding the evidence is for that person to understand the fact that this evidence is more preponderant than his misconception ... such as when someone says, 'He is not convinced that this evidence is stronger than the misconception that he has'; this is not a condition. The permission that is required to understanding the evidence is the first kind, which is understanding the meaning, understanding the significance of the verse in Arabic, and so on. As for understanding the evidence in the sense that this evidence is most likely to be applicable and is a stronger evidence for the falsehood of worshiping other than Allaah or for the invalidity of falsehood, then this is not a condition; what is important is that he should understand its meaning and significance; after that, Allaah leads astray whom He wills, and guides whom He wills."

Finally, we notice from your questions that you suffer from obsessive whisperings in regard to matters of disbelief and faith; so we advise you to stay away from them and not get carried away with them as this is a widespread evil.

Allaah knows best.