Why is religious belief so hard to accept? Why is it so much harder to accept today than in past centuries?
Herewith, some notes toward a list of the impedimenta, the stumbling blocks, that litter the path of the would-be believer of the present day. Whether the following ought to be impediments is a further question, a normative question. The following taxonomy is merely descriptive. And probably incomplete. This is a blog. This is only a blog.
1. There is first of all the obtrusiveness and constancy and coherence of the deliverances of the senses, outer and inner. The "unseen order" (William James), if such there be, is no match for the 'seen order.' The massive assault upon the sense organs has never been greater than at the present time given the high technology of distraction: radio, television, portable telephony, e-mail, Facebook and other social media, not to mention Twitter, perhaps the ultimate weapon of mass distraction.
Here is some advice on how to avoid God from C. S. Lewis, "The Seeing Eye" in Christian Reflections (Eeerdmans, 1967), pp. 168-167:
Avoid silence, avoid solitude, avoid any train of thought that leads off the beaten track. Concentrate on money, sex, status, health and (above all) on your own grievances. Keep the radio on. Live in a crowd. Use plenty of sedation. If you must read books, select them very carefully. But you'd be safer to stick to the papers. You'll find the advertisements helpful; especially those with a sexy or a snobbish appeal.
If Lewis could only see us now.
2. The fact that there are many competing systems of religious belief and practice. They overlap, but they also contradict. The extant contradictory systems cannot all be true, though they could all be false. The fact that one's own system is contradicted by others doesn't make it false, but it does raise reasonable doubts as to whether it is true. For a thinking person, this is a stumbling block to the naive and unthinking acceptance of the religion in which one has been brought up.
3. The specificity of religious belief systems and their excessively detailed dogmatic contents. One is put off by the presumptuousness of those who claim to know what they cannot, or are not likely, to know. For example, overconfident assurances as to the natures of heaven, hell, and purgatory together with asseverations as to who went where. Stalin in hell? How do you know? How do you even know that there is a place of everlasting punishment as opposed to such other options as simple annihilation of unrepentant miscreants?
There is the presumptuousness of those who fancy that they understand the economics of salvation to such a degree that they can confidently assert that so many Hail Mary's will remove so many years in purgatory. For many, such presumptuousness is an abomination, though not as bad as the sale of indulgences.
The human mind, driven by doxastic security needs, is naturally dogmatic and naturally tends to make certainties of uncertainties. (It also does the opposite when in skeptical mode: it makes uncertainties of (practical) certainties.)
Related post: Are the Dogmas of Catholicism Divine Revelations?
4. The fact that the religions of the world, over millenia, haven't done much to improve us individually or collectively. Even if one sets aside the intemperate fulminations of the New Atheists, that benighted crew uniquely blind to the good religion has done, there is the fact that religious belief and practice, even if protracted and sincere, do little toward the moral improvement of people. To some this is an impediment to acceptance of a religion.
Related point: the corruption of the churches.
Again, my task here is merely descriptive. I am not claiming that one ought to be dissuaded from religion by its failure to improve people much or to maintain itself in institutional form without corruption. One can always argue that we would have been much, much worse without religion. Even Islam, "The saddest and poorest form of theism," (Schopenhauer) has arguably improved the lot of the denizens of the lands in which it has held sway, civilizing them, and providing moral guidance.
5. The putative conflict between science and religion. Competing magisteria each with a loud claim to be the proper guide to life. Thinking people are bothered by this.
6. The tension between Athens (philosophy) and Jerusalem (religion). The battle between faith and reason. So many of the contents of religion are either absurd (logically contradictory) or else difficult to show to be rationally acceptable.
7. The weight of concupiscence. We are sexual beings naturally, and oversexualized beings socially, and so largely unable to control our drives. The thrust of desire valorizes the phenomenal thus conferring plenary reality upon the objects of the senses while occluding one's spiritual sight into the noumenal. See Simone Weil in the Light of Plato. Is it any surprise that the atheist Russell, even in old age, refused to be faithful to his wife? It is reasonable to conjecture that his lust and his pride -- intellectuals tend to be very proud with outsized egos-- blinded him to spiritual realities. Jean-Paul Sartre is another case in point.
8. Suggestibility. We are highly sensitive and responsive to social suggestions as to what is real and important and what is not. In a society awash with secular suggestions, people find it hard to take religion seriously.
9. The apparent moral absurdities of some religious doctrines. See Kant on Abraham and Isaac.
10. The rise of life-extending technology. For some of us at least, life is a lot less nasty, brutish, and short than it used to be. This aids and abets the illusion that this material life suffices and will continue indefinitely. The worst illusion sired by advanced technology, however, is the transhumanist fantasy which I discuss here.