Look at how Allah describes the mentality of disbelief in the Quran and how closely it resembles what we hear from atheists and others today:

(6:25) And among them are those who listen to you, but We have placed over their hearts coverings, lest they understand it, and in their ears deafness. And if they should see every sign, they will not believe in it. Even when they come to you arguing with you, those who disbelieve say, “This is not but legends of the former peoples.” (6:26) And they prevent [others] from him and are [themselves] remote from him. And they do not destroy except themselves, but they perceive [it] not. (6:27) If you could but see when they are made to stand before the Fire and will say, “Oh, would that we could be returned [to life on earth] and not deny the signs of our Lord and be among the believers.” (6:28) But what they concealed before has [now] appeared to them. And even if they were returned, they would return to that which they were forbidden; and indeed, they are liars. (6:29) And they say, “There is none but our worldly life, and we will not be resurrected.” (6:30) If you could but see when they will be made to stand before their Lord. He will say, “Is this not the truth?” They will say, “Yes, by our Lord.” He will [then] say, “So taste the punishment because you used to disbelieve.”

Atheists often claim that all believers need to do is provide some empirical proof and that’s all they will need to believe in God. What is amazing is that Allah says that even if, after seeing the Fire with their own eyes and acknowledging their Lord directly, the disbelievers were returned to life on earth, they would also return to denial. So empirical proof is clearly not the issue. Denial and concealing what one sees and experiences in the world and in one’s self is the problem, indeed the biggest and gravest problem.