Paul Brunton, Notebooks, Volume 12, Part I, p. 96, #14:
He alone can be an atheist who has never experienced a glimpse, or who has been caught and become embedded in a hard dry intellectualism, or in whom ethics and conscience have withered.
The point is defensible if put in less ringing terms. Most atheists have either (1) never had a religious or mystical or paranormal experience, or (2) have succumbed to the hypertrophy of the critical faculty, or (3) are bereft of conscience or moral sense, or all three or any two of the above.
Ad (1). A prosaic fellow, earth-bound, who believes only in the visible, the tangible, and the edible, who has never had an unusual experience of the sort that intimates a reality beyond the sensible, or beyond the grossly sensible, will of course not be inclined to take seriously the claims of religion or the beliefs in God and the soul. He believes in what the outer senses reveal to him and will be inclined to dismiss as incredible the belief that there exist things external to his consciousness that are not certifiable by the five outer senses or by the instrumental extensions (telescopes, etc.) of the five external senses. If he had had a mystical experience or a religious experience or a paranormal experience such as an out-of-body experience then he might have been budged from his narrow empiricism. But lacking these sorts of experience, he sees no need to believe in anything but the objects of sense experience and such scientific posits as may be necessary to explain their behavior.
Our prosaic worldling's attitude is not irrational. He bases himself on what is given, but what is given to him are only the deliverances of the outer senses. He is aware of various a posteriori arguments for the existence of God but they find no purchase with him. For the sheer obtrusiveness of the sense world makes it impossible for him to believe in anything beyond it. And in a battle between the massive testimony, at every waking hour, of this gnarly world of time and change, and the output of abstract reasoning, the former is sure to win in the mind of our sense-bound worldling. And so he uses his intellect to resist the arguments, making of each modus ponens a modus tollens.
And of course there is that not unimportant matter of our worldling's enslavement to the pleasures of the flesh. As Plato observed, each pleasure and each pain does its bit to pin the soul to the body so securely and in such a manner that nothing can be real to such an enslaved soul except that which has a bodily nature. (Phaedo St. 83) Our man may even have had a mystical or religious or paranormal experience or two; but they will be no match for his ground-conviction of the ultimate reality of the material world, a conviction made impossible to break because of his attachment to sensuous pleasure.
Ad (2). A dessicated intellect honed on the whetstone of analysis and powered by the will not to believe will have no trouble finding reasons for disbelief. Anything can be argued, and any argument can be turned aside. Reason in us is a frail reed indeed, easily suborned by the passions and other irrational factors.
Ad (3). Can an atheist be moral? Well of course. There are plenty of atheists who are more moral that some theists, e.g., Muslim terrorists. A different and much more interesting question is whether atheists are justified in being moral. I pursue this question in Sam Harris on Whether Atheists are Evil. And then there is the matter of conscience. What exactly is it? Atheists are typically naturalists. Is there a decent naturalistic theory of conscience? Could there be? Or is the fact of conscience in us not an indicator of our higher origin? And so while it is not true, pace Brunton, that atheists lack a conscience, I would argue that (i) their atheism prevents them from fully plumbling the depths of its deliverances, and (ii) they are in no position to provide an adequate theory of conscience and its normativity.
