We've all heard the term a thousand times, and one could probably say what has been said of many systems, namely, that there are as many definitions of fundamentalism as there are people using the term.
So let me today clarify the way that I use it as opposed to more historic uses. These historic uses were once matters of defining historic orthodox Christianity in light of nineteenth century liberalism. I, and any other orthodox Christian, am in some way a fundamentalist in this sense. When the Church did this, it was functioning as it should, clarifying its message in light of new heresies and apostasies.
But the term has evolved from this and now means something different.
Now, I do not use the term as the media does. Most of the media, and often liberal academia, uses the term in two ways: (1) to refer to people who have as their authority an outside source to themselves to which they devoutly adhere (i.e., religious conservatives of any sort), or (2) people who dogmatically believe and proselytize others in those beliefs.
However, I don't use the term in any of these ways. Instead, I choose to reserve it for all devotees of any worldview (i.e., regardless of ideological persuasion), although my use is equally pejorative. So what is a fundamentalist to me?
Christ once said that if the eye is dark, the whole body will be. A fundamentalist in my mind is someone who has a dark eye. He has not been trained to think critically of his own views. He cannot see his presuppositions and ultimate beliefs, and hence, he argues as though what he says is matter-of-factly true, even if what he believes is refuted by his own sources of authority, which are usually his own reasoning out of whatever authoritative source he values. He speaks dogmatically about that which he assumes to be true, but does not know that he assumes.
But I would add to this that most fundamentalists, again, according to my use of the term, don't want to bother to represent the other person's view accurately when critiquing it. They use a lot of strawmen and ad hominems in place of arguments.
In this regard, fundamentalists are dangerous, not because they make us think, but because they make us dumber. If iron sharpens iron when two critical thinkers of opposing opinions meet, then a meeting with a fundamentalist is like the clashing of iron upon cottonballs. The sword is not sharpened and the cottonball just turns into a million more little cottonballs, multiplying the faith of the fundamentalist in foolishness rather than changing him for the better.
In other words, I think the term "fundamentalist" to me simply means "unteachable." He's not a person willing to learn what his source of authority really is, what it can and cannot tell him, and whether he's understood it correctly. He just knows already, even in the face of evidence to the contrary--even in the face of evidence from his authoritative sources to the contrary.
He's not someone who is rigid in his beliefs. EVERYONE is rigid in his or her beliefs. Only fundamentalists, liberal or conservative, think otherwise. What I am saying is that he is not even teachable to the sources of authority he recognizes simply because he does not have a critical mind toward evaluating himself, his own ideas, where they come from, whether they are firmly established appropriately given his own sources of authority, etc. And he doesn't do this because he isn't humble. He thinks highly of himself enough to just keep on keepin' on, regardless of his misuse of the very authorities to which he says he is committed.
Hence, there are atheists who are fundamentalists, their sources of authority supposedly being logic and science. There are Islamic fundamentalists who attempt to use logic and the Quran. There are Christian fundamentalists who attempt to use logic and the Bible. There are even agnostic fundamentalists who just attempt to use logic and their own experience. Notice that everyone is using logic in their attempt to reason out and arrange their lives and thoughts according to a source of authority, whether experience, science, a holy book or tradition, etc.; but the fundamentalist is usually lacking in his ability to use logic, which is why I say he "attempts" to use it. But this means he will often misconstrue what his source of authority really says, since he is incapable of using logic that would arrange and organize that authoritative source in a way that cooperates with its real message and therefore would interpret it correctly.
Hence, the fundamentalist is one who has a deficiency in his own sources of authority. It is not simply that he does not believe the same as you. There are many non-fundamentalists who do not believe the same as one another. Instead, it is that he is incapable of evaluating whether his own views are consistent with his own sources of authority and the logic he uses to reason those authorities out. But it is not merely the deficiency of these that makes him a fundamentalist. This inability must be joined by hubris that gives him an unteachable disposition, so that his deficiency is never made sufficient. His lack of ability is never corrected to the point of ability. He is forever right in his own mind, though all that he pretends to believe are his sources of authority scream otherwise. In reality, he is his own cult leader, and one that will bring himself to ruin at that. For if the eye is dark, the whole body will be.