The original use of the term 'fundamentalist' arose early in the 20th century among Protestant theologians reacting against liberal, social-gospel Protestantism. The Fundamentals: A Testimony To The Truth, an anthology of essays published in 1915, reasserted certain doctrinal tenets, "fundamentals," that many theologians increasingly felt a need to defend. The most widely stressed were: the inerrancy of Scripture, sola Scriptura, subsitutionary atonement by means of Jesus' crucifixion, and the bodily resurrection of Jesus. Under the influence of John Nelson Darby, whose dispensationalism remains quite influential today even outside fundamentalist circles, belief in the imminence of the Second Coming was also given renewed importance. It wasn't long before the term 'fundamentalism', in the sense just described, got to name the faith of a great many American Protestants and some British Protestants; the crucible was William Jennings Bryan's attack on the theory of evolution at the Scopes trial in 1925. Even today, the term retains some clarity when used in roughly that way. But nowadays it is typically used a synonym for religious extremism of almost any variety; thus are al-Qaeda and Pat Robertson, the Taliban and the evangelicals, tarred with the same brush. And the "new atheists" aren't the only ones who do that. In the mainstream media, it seems to be taken for granted that the only respectable, Western religious alternative to "fundamentalism," understood as religious extremism, is the sort of approach that the original Protestant fundamentalists were reacting against a century ago.
I call that approach 'modernism' in keeping with the strain of Catholic thought that Pope Pius X and his conservative allies were rejecting at roughly the same time as the "fundamentalists" were rejecting liberal Protestantism. In his notorious encyclical Pascendi Dominici Gregis (1907), the Pope termed Modernism "the synthesis of all heresies," insisted on a neo-scholastic intellectual formation for seminarians, and launched what was to become a virtual witch-hunt against Catholic clergy and intellectuals suspected of Modernism. When I first read Pascendi as a college student, I remember agreeing with much of it. Many of the ideas it denounced had resurfaced, in slightly different forms, among my half-Catholic contemporaries, and they seemed to me pretty much as destructive as the Pope had said. But as things turned out, one of the problems with Pius X's approach was that it merely buried, for a time, intellectual problems that needed to be tackled head-on, as John Henry Newman had done by how he mounted his case against "liberalism" in religion. Almost as bad, Pius X's approach mistakenly identified a particular kind of liberal thinking as the problem, when the real problem was much broader and remains very much with us today.
The problem is one that modernism, of whatever variety, actually shares with Protestant fundamentalism (and, I suspect, with Muslim fundamentalism too; but that's another discussion). By rejecting the idea of an infallible teaching authority within the Church—i.e. a Magisterium, as understood by the Catholic Church—both render the distinction between divine revelation and human ideas effectively nugatory.
Notice I do not say that they deny the distinction; most accept it in principle, and the fundamentalists insist on it. Indeed many Protestants, especially fundamentalists, object that they consider "Scripture alone" to be the "infallible" authority within the Church. And Catholics are obliged to agree that Scripture contains, at least materially, all the truth God willed to reveal to us. But both history and logic confirm Pontificator's Second Law: "When the Bible alone is our authority, the Bible ceases to be our authority." That is why Protestant modernism arose; Protestant fundamentalism was merely the reaction of those with residual faith against that consequence. But such fundamentalism remains intellectually powerless against it.
If sola Scriptura is our de jure authority, then there are as many de facto authorities as there are ecclesial bodies adhering to different interpretations of Scripture. By hypothesis, no such body can even claim the authority to adjudicate definitively for all the other bodies among the circulating interpretations. Often rejected as a tired staple of Catholic apologetics, that assertion is typically countered by the claim that Scripture is self-interpreting. It is true that any given passage of Scripture can and must be interpreted in light of the canon as a whole; in that sense, Scripture is unavoidably self-interpreting. But if the claim that Scripture is self-interpreting be taken to mean that there is some compendious "plain sense" of Scripture that every believer can and must take as the content of divine revelation, without reference to some further authority, then that claim is false simply as a matter of historical fact. For Tradition predated Scripture as a rule of faith; it was the official custodians of the Church, the bishops, who consulted their understanding of the former so as to gradually determine what belonged in the latter; and as conflicting interpretations of both arose over time, it was the same authorities as a body who settled conflicts that became church-dividing. Scripture, Tradition, and the Magisterium stand or fall together. Without all three, the most we can assimilate is a cross-spectrum of human opinion about divine revelation—not Revelation itself. And that is why there are almost as many Protesant denominations as opinions.
It doesn't have to be that way, of course. Protestantism originally arose as a reform movement within the Catholic Church. That is why Ben Myers, a fairly liberal Protestant theologian, recently quoted the following with approval:
...protestantism is always the question, the objection, the provisional mode of protest that takes place within the wider presupposition of the givenness of the Catholic church. It is always protestants who must justify their identity as non-Catholics rather than the other way round...we cannot assume the perpetual existence of protestantism. We must be open to the possibility of the end of protestantism if we are to be true to the aims of the Reformers themselves.
That post provoked a rather interesting discussion that I would have liked to see continued. One thing I noticed about the discussion that did occur, however, was that none of the objectors to the post got to the heart of the matter. Defending the post, the Pontificator wrote in its combox:
What perhaps is most lacking in this thread on catholicity is the spirit of catholicity. To be catholic, I propose, is to trust in the Church and thus be willing to subject one's opinions to the judgment of the Church.
Thus Kim writes:
"My problem is not that the Roman model of unity is institutional, it is that it institutionally enshrines disunity (de jure I mean, we all express disunity de facto), e.g. Michael's examples of the exclusion of women from the ministry of word and sacrament and the theological pathologising of homosexuals (and this, of course, goes for many Protestant churches too)."
This is a remarkable claim; indeed, it is a Protestant claim. Kim would have us believe that those Churches...that adhere to the traditional teaching of the Church on the the ordination of women to the priesthood/episcopate and the restriction of sexual intercourse to the bonds of Holy Matrimony are guilty of instutionalizing ecclesial disunity. I'm sorry, but this is ridiculous. This is nothing but private judgment run amok.
If catholicity means anything it means that at some point we finally must trust in the judgment of the Church. Without such submission, ecclesial unity is impossible. Newman saw this clearly.
I agree, and the two responses to that comment did not come to grips with it. Thus the first response said that it is sin which hampers Church unity, which nobody disputes; the second pointed out that many opinions are allowed even in the Catholic Church, which again nobody disputes. Citing such facts does not constitute an argument against the Pontificator's point, which has been missed altogether. The point is that, in order to recognize and assimilate the revelation in Jesus Christ, we need a visible authority to speak in his name, and we need to submit to that authority when it claims to speak in his name. Otherwise we are left only with opinions—and, inevitably, institutionalized disunity.
In media parlance, fundamentalists are people who adhere to certain ancient tenets in reaction against "liberalism" in religion, or what was once called "modernism." But the modernists are simply those who take the Protestant principle to its natural conclusion. If, in the final analysis, we need not submit our judgment to that of the Church when she speaks with her full authority, then religion is ultimately a matter of human opinion. Opinions can and do change, which is precisely what the phenonomenon of modernism represents; observe what's been happening in the Episcopal Church. One can indeed move from modernism to fundamentalism, thus aligning one's religious opinions somewhat more closely with the content of divine revelation; that in fact what the Anglican "reasserters" have been doing. But there's nothing in Protestantism, even in principle, to rule out going the opposite way. The reasserters, of whatever denomination, happen to be right in certain instances; but they do not, because they cannot, claim to speak with the infallibility of Christ himself.
Because of the Magisterium, the Catholic Church steers between the Scylla of fundamentalism and the Charybdis of modernism. By rejecting the former, she acknowledges the facts of history and remains open to the future, as the modernists try to do; by rejecting the latter, she preserves in its fullness the "faith once delivered," as the fundamentalists try to do. Only that stance is defensible; only that stance is worth defending.