Imam Ali (a) is reported in Nahjul balagha to have said:
Doubt is named doubt (al-shubhah) because it resembles truth. As for lovers of Allah, their conviction serves them as light and the direction of the right path (itself) serves as their guide; while the enemies of Allah, in time of doubt call to misguidance in the darkness of doubt and their guide is blindness. One who fears death cannot escape it nor can one who loves eternal life secure it.
I'm going to go with this a bit. Let us divert ourselves from the good old Atheist vs Theist debate for a second.
A person is shown that a verse says this and that, and it's clear, but often, we see disbelief takes on the form of:
"Well I myself don't accept it, a lot of people don't accept it, so it must be unclear and God could've said something else (more clear), and God if he wanted us to follow this and that, would've said it a more clear way."
The problem that occurred with Mohammad (s) is that his signs were very bright in form of miracles, but they would say, why isn't he given the like of Messengers before, despite the fact, he was given miracles and signs, and they accused him of sorcery. In other words, no matter what sign he brought, to them, the past miracles were always better, even though his signs were often even bigger signs than of the Prophets (a) of the past.
Going back to debate between Theists and Atheists, often, an atheist makes in the form of:
"Well I myself doubt if I have objective value, I don't see it clearly like you, therefore, you must be believing it on blind faith in some way or otherwise I would see it like you"
This is a terrible problem with humans, when they take their blindness as proof that a proof is not clear.
Mohammad's (s) people, all the miracles they were shown, often, would say (some believed, most did not), why aren't you given signs like those before you and would accuse his signs of being works of sorcery. This was not due to his signs being less in greatness then those before him and less bright, nor due to genuine sincere doubt of the people opposing to it.
Similarly, I believe Ahlulbayt (a) position is often clarified clearly in Quran and Sunnah, but people take their disbelief and blindness as proof it's not proven.
This is a vicious circle.
