1. Avoid intellectual myopia.
Intellectual myopia occurs when you latch onto one idea too strongly. That one idea either becomes the prism through which you filter all other issues or it becomes the only issue you devote your time to.
How do you know whether you’ve fallen victim to intellectual myopia? One of the most common symptoms of myopia is the lurker mentality. The lurker is a person who frequents websites only to see if those websites are posting on their pet issue. This is the guy who latches onto a particular scientific theory and lurks around websites, sometimes hiding quietly in the shadows for months, just biding his time until the subject comes up or is at least skirted around enough so that he can pounce out of the shadows and wage his war against all nay-sayers. You can find these guys lurking around the Gospel Coalition or Challies.
Another symptom of intellectual myopia is the call to arms brigade. These are the persons who usually spend their internet time loitering around a website or group of websites that are devoted to their pet issue. When they find that some other site has said something regarding their issue there is a call to arms and suddenly defenders of said issue are crawling out of the wood work. Annihilationists tend to fall into this category, in my experience. Maybe a better example would be the homosexual activists.
While myopia can manifest itself regarding almost any issue, it can be especially pervasive among people who adopt heretical or at least heterodox positions. For instance, there is a well known blogger and lurker who we’ll call Tale Duggy who seems to have it as his sole goal in life to argue for Unitarianism. He will randomly appear at websites only on the occasion that those websites mention something about the deity of Christ.
Another symptom of intellectual myopia is the doomsday mentality. If you think Christianity is going to go the way of the dinosaur unless Christians come to embrace your issue (e.g., acceptance of gays, acceptance of an old earth, acceptance of evolution, works based salvation) then you might be suffering from intellectual myopia. Conversely, if you think Christianity would experience unprecedented revival if Christians just came to embrace your view then you might be suffering from intellectual myopia.
Myopia is problematic because ideas tend to be interconnected. Developing the skill of critical thinking is aided by thinking about a variety of issues and not just by thinking about one thing intensely. A good idea in theology may carry over to politics and vice versa. A good argument about one ethical issue may have applicability to constructing or deconstructing an argument in a different ethical issue or in a political issue. People who only know one issue often have blind-spots even regarding the one issue that they are intensely focused on.
2. Avoid intellectual isolation.
Intellectual isolation can occur independently of intellectual myopia. One can have a balanced set of interests (which does not mean everything is found to be equally interesting) and still be intellectually isolated. This occurs when the person never interacts with arguments from the opposing side and never engages colleagues in discussion or debate.
I’ve emphasized the word “interacts” because intellectual isolation can occur even when a person does read some of what the other side is saying and even occasionally ventures forth to engage the enemy. One symptom of such isolation actually manifests itself on the occasion of an intellectually isolated person attempting to engage opponents: self-refutation. This is the use of arguments against a position which in fact end up refuting one’s own position. Again homosexual activists provide a common example. They often use arguments and rhetoric in favor of same-sex marriage that would undercut their own opposition to other forms of marriage. I commonly run into the intellectually isolated theistic evolutionist: the person who uses the God-is-a-deceiver argument against YEC, while holding to a reading of Scripture that opens themselves up the exact same charge.
Another symptom of intellectual isolationism is hyper-sensitivity. If you find yourself constantly being offended by perceived insinuations in analogies to incest, you might be an intellectually isolated homosexual activist. If you find the very statement of the opposing argument is offensive or bigoted or racist or sexist, you might be intellectually isolated. If you think everyone who disagrees with you is either (a) intellectually dishonest or (b) suffering from some phobia (e.g., homophobia), you might be intellectually isolated.
Isolationism is problematic because people who think differently than we do can help us see both the weaknesses and the strengths in our position. No one has the market cornered on reason (with apologies to New Atheists) and interacting with other rational agents can help us see where we’ve failed to be reasonable.