A religion or philosophy can have two kinds of problems: internal and external.
Suppose atheism (for example) can make perfect sense of the natural world, but lacks coherence, having only weak explanations for the very philosophical assumptions that make its “science” possible. If this were the case (I am not arguing it is), then that would be an internal problem.
Suppose theism is coherent, but cannot make sense of much of the external world. This would an external problem.
Both kinds of problems can be more or less serious. A serious “external problem” would be one where the thing that is not being explained is important to both the predictions of the philosophy and to reality. In like manner, a serious “internal problem” would be one where the incoherence is regarding a central plank of the world-view and the contradiction is impossible to get rid of by modifying the two ideas.
Every view of reality of which I am aware has problems. Most have both external problems (things that don’t match what is predicted outside the theory) and internal problems. Atheism has problems, naturalism has problems, and so does traditional Christianity. One ends up picking the problems one prefers! Of course this must be done carefully and rationally, but there is no good in pretending that the day is coming when every problem will go away.
What would be the fun in that?
When you meet someone, whether a Darwinist, a Platonist, or a Christian, who has no doubts or intellectual puzzles and nothing but contempt for the strengths of other world views . . . that person is no friend of a free and enlightened human.
First, let’s clear away a common confusion. Many people simply assume that “external reality” is exhausted by matter and energy. The outside world may contain more, much more . . . including mathematical objects, gods, ideas, angels, and human souls. (The existence of the material world has been disputed by philosophers such as Berkeley, but I shall not consider these views.) If there is good evidence for such objects, then they too need explanation. A theory that makes sense of one sort of real thing at the expense of being able to explain another has a problem.
For example, suppose there is a decent argument (let’s say the ontological argument) for God’s existence that does not depend (at all) on science. If one combines that with personal, internal experience, then this seems good grounds to be at least skeptical about any philosophical system that attempts to “explain away” God. If there is decent reason to think “God” is part of the external world that must be explained, then any good theory about reality should do so.
One philosophical problem with dealing with the “external” reality is trying to decide what is really there that needs explaining. Tools like science are useful for some kinds of explanation, but unless one assumes (and this assumption strikes me as very dubious) that one can explain everything with science, then it will have certain limitations and blind spots.
Some useful tools become useless when they reach the limits of what they were designed to do.
What should we do with beliefs that seem incoherent (like those of the hypothetical atheist above) or have “external world” problems?
It would be rash to simply dump a philosophy or view of the world based on just having such a problem. Nobody would have a world-view for very long if that was the strategy! First, the severity of the problem would have to be measured. Second, the seriousness of the doubt in the context of the system would have to be weighed.
In the case of tiny cult groups, there exists a very simple view of reality. They might suppose (for example) that a comet was coming with a space ship to carry them all off to a happy planet on the other side of the cosmos. When that comet comes, failure to see the ship should lead to a serious examination of the reasons to believe in the cult in the first place. The central belief of the cult is under assault. Deny that belief and there is nothing left. In the very nature of a cult, there is no ability to hold their “fringe” beliefs provisionally, since all their beliefs are fringe!
They do not accept that things are “going against them” and consider their options. It might be rational to persist in the general belief if there were reasons independent of the “comet thing” for accepting the authority of the cult in the first place. However, even then the cult must recognize that it has a serious problem with the “comet/ship” portion of belief and work hard to resolve the problem. These problems must be openly acknowledged and the idea moved to the “intellectual speculation” bin for further work.
The problem with most cults is that they have such simple belief structures. They are much less resilient than an older view such as atheism. One mark of a cult (in fact) is too high a level of “faith” in the system . . . like some radical Darwinists who cannot imagine any merit to any criticism of their world-view from any perspective. It is a bad idea to base strong faith and strong actions (like the suicides of the comet cult) only (or almost only) on personal experience.
A religion like Christianity has several lines of argument for the existence of God and many beliefs with different levels of importance. This allows some room for speculation and intellectual commitments that otherwise have serious problems.
In general, I am content to allow my secular friends to “work on” a highly provisional belief they might hold, if there are some decent intuitions or reasons to persist. I am often amazed (and made a little sad) by people (religious and non-religious) who are such conformists that there is no area on the “edge” in which they are willing gamble a bit!
We want to leave room for thinkers (of all sorts) to adopt provisional theories on the margins of their philosophy in order to “try them out” and hold them with enough vigor in order to see if sense can be made of them.
The best examples of this sort of idea for a traditional Christian would be views about certain details regarding the “end times,” a young earth view, or some theory about the nature of angels. As a young earth proponent, I am dealing with a view at the edge of importance to the Christian view of reality. It is also implausible given best modern science. This is very serious concern and should be the subject of hard labor such as that begun by researchers like Kurt Wise.
The good news is that if young-earth creationism fails, it will not impact Christianity. If C.S. Lewis could be “old earth,” I am confident I could survive such a “switch!”
On the other hand, perhaps our entire view of reality is too simple or our assumptions (at a very deep level) are wrong in science. Science is not (after all) the only knowledge tradition. Religion is a knowledge tradition as is metaphysics. Since religion (in this case Christianity) and philosophy point to problems with an older cosmos, it is proper for a Christian to provisionally adopt a view to challenge it. This is not central to his theism, his Christianity, or his view of reality.
The cultist or extremist shows no such modesty. He either adopts majority opinion in every case to play it safe or he refuses to admit that any idea he holds is in trouble at any given moment. One person is epistemologically stale and the other irresponsible. Of course, areas where a man is willing to “cut loose” will depend on other metaphysical commitments.
In no case should a person “lead with their speculations.” Nobody should be forced to teach these ideas and they could never be a good reason to accept a view. They (also) cannot be the basis for high-risk action (like committing suicide to join the comet mother-ship).
Any world view should lead with their strengths. I am a traditional Christian because best reason and philosophy made me one (against my own wishes). If Christianity is true, then there are some interesting speculations possible at the edges. That would be true (of course) if I were a member of any other religion or secular philosophy.
There is an odd kind of Christian who cares nothing about science and does not care when the scientific consensus disagrees. There is an equally odd kind of Christian who tailors his theology to whatever the contemporary scientific view is. Instead, the sophisticated Christian balances all the sources of knowledge, all disciplines to develop a world view.
A good sign of cult is when they see the “other” and find no merit in their ideas. “Christians” who see nothing attractive in secularism or a Darwinist who can deal with a first-class philosopher such as Al Plantinga only in disrespectful polemic are examples of this tendency.
So in the end, when should we give up on an idea? We should give up on an idea when it demands serious action based on insufficient evidence . . . such as the comet cult group. We should hold on when it is proving intellectually interesting and the cost is not too high. Nearly as bad as pressing on with an idea inappropriately is the poor soul who cannot understand why someone would want the freedom to speculate.
Early in graduate school, I received the very good advice to “follow the argument wherever it leads.” This has stood me in good stead thus far, brought me interesting friends, good intellectual puzzles, and humility in the face of all that I do not know.