Kreeft writes,

So the claim that we can know that there is no God logically implies that the person who makes that claim has omniscience, that is, is God.

This is not what reductionists claim, or at least, they need not (I would say, should not) claim to know that there is no God. Kreeft's "refutation of reductionism in general" is a case of strawmanning.

I know some who clearly do such, actually.

That doesn't answer the question I asked.

The person who seriously denies the existence of the sun is either committed to a way of thinking that he refuses to abandon, even to the point of insanity, or he is mentally ill.

I didn't ask for an evaluation of people who deny the existence of the sun. I asked why no such people are known to exist.

I know some who clearly do such, actually.

Christi pax.

No. The person who seriously denies the existence of the sun is either committed to a way of thinking that he refuses to abandon, even to the point of insanity, or he is mentally ill.

Christi pax.

(how can I choose to be an atheist if I don't know what that is?)

But you do know. So could you be one just by wanting to be one?

the will can influence the mind to go so far as to ignore information in order to reject a conclusion

So, the only reason nobody denies the sun's existence is that nobody wants to deny it?

No one can make me worship the Sun, unless worship is defined as going through the motions

Yes, they can make you go through the motions, and that was my point. Behavior can be compelled. Thinking cannot be compelled.

But nobody, sun worshiper or not, has ever denied the sun's existence, and that unanimity of belief is not the result of any compulsion.

Descartes did at the beginning of his Meditations.

It was a thought experiment. By definition, it didn't really happen. If your response is: But he said he really did it, then my counter is: I don't think he meant it literally, and if he did mean it literally, then I just don't believe him.