It is often lamented that modern (or postmodern) evangelicalism does not look to the past for the foundations of its faith and practice. While this is certainly true in a strict sense, there is no escaping the universal truth expressed in Ecclesiates 1:9 and the fact that evangelicals today owe a lot to the legacies of those who've pandered a notion of mere Christianity in the past.
Claiming to get at the kernel and leaving behind the husk, these seemingly "radical" innovators are actually no more than current expressions of a rebellious individualism that has marked heretics of a bygone era. Tradition is stiff, "new measures" are where the Spirit's at, doctrine divides, and a host of other meaningless catch phrases comprise their rhetoric.
In fact, "Christian liberalism" is mere Christianity and this is what J. Gresham Machen fought against, not liberalism per se.
To C.S. Lewis fans this little snippet from Dr. Carl Trueman has much to say:
Now, when one approaches the major texts of postmodern evangelicalism and asks what they are saying, the answer is exciting: they claim they are opening up radical new directions for theology; but when one approaches the same texts and asks what they are doing, the answer is somewhat more prosaic. Far from pointing to new ways of doing theology, these texts are on the whole appropriating an admittedly new idiom, that of postmodernism, in order to accomplish a very traditional and time-honored task: they are articulating a doctrinally minimal, antimetaphysical 'mere Christianity.' Like pouting teenagers in pre-torn designer jeans and Che Guevara tee-shirts, they look angry and radical but are really as culturally conformist and conservative as a tall latte from Starbucks.
Any historian worth his salt can see that this 'mere Christianity' agenda has a well-established pedigree in Christendom. At the time of the Reformation, Erasmus, writing against Luther, used a combination of Renaissance skepticism, intellectual elitism, and contemporary Catholic teaching on church authority to argue for a Christianity which was essentially practical in orientation and minimally doctrinal in content. In seventeenth-century England, Richard Baxter adopted a linguistic philosophy suggestively akin to that of his contemporary Thomas Hobbes in order to undercut the traditional metaphysical basis of Christian orthodoxy and offer a minimal account of the doctrines of the faith. In the early nineteenth century, Friedrich Schleiermacher responded to Kant's critical philosophy by fusing pietism, Romanticism, and a post-Kantian antimetaphysical bent to reconstruct Christian doctrines as statements about religious psychology, not transcendent theological truths. And evangelicalism, from its roots in revivalism and pietism, through its development in the pragmatic, anti-speculative culture of America, to its current existence as a more-or-less amorphous, transdenominational coalition, has historically embodied in its very essence an antipathy to precise and comprehensive doctrinal statement. To make the point of immediate relevance in a Westminster context, it was this kind of evangelical position, and not really true liberalism in the technical sense, against which Machen was fighting at Princeton prior to 1929. Therefore, it would seem at least arguable from the perspective of history that the evangelical appropriation of certain aspects of postmodernism is not really a radical break with the past. It might simply be a co-opting of the latest cultural idiom to give trendy and plausible expression to a well-established and traditional ideal of 'mere Christianity.'
Let me interject a clarification at this point lest I be misinterpreted as saying that mere Christianity is something wrong in itself, a matter to be despised. That is emphatically not what I am saying at all. Salvation does not depend upon the individual's possession of an elaborate doctrinal system or a profound grasp of intricate and complex theology. Yet this is not my point. What I am claiming is that mere Christianity, a Christianity which lacks this doctrinal elaboration, is an insufficient basis either for building a church or for guaranteeing the long-term stability of the tradition of the church, that is, the transmission from generation to generation and from place to place, of the faith once for all delivered to the saints. What is disturbing is that the advocates of postmodern mere Christianity are not debating how much one must believe to be saved; they are actually proposing a manifesto for the life of the church as a whole, a somewhat more comprehensive and ambitious project. It is the validity of this that I question. (Rage, Rage Against the Dying of the Light, WTJ 70 : 4-6)