In the Göttingen Dogmatics, Karl Barth wrote that "No one reads the Bible directly. We all read it through a set of glasses, whether we want to or not..." Biblicism is the use of the Bible against Church History, and it is preference one's private interpretation of the bible over and against what the Church has taught about the bible over the past two thousand years and everywhere. It is an amazing bravado when a person is willing to interpret the Bible in a way that no one has said before, and in opposition of all of the Fathers of the Church from the beginning and until now! This bravado is typically justified by believing that this private interpretation is a match between the Word of God in the Bible vs the errors of men in Church History. But, the reality is that Bible is always read through the categories of our mind that we impose on the world (i.e. Kant), such that it is never the bible vs Church History or father so-and-so, but rather it is my private interpretation of the Bible verse two thousand years of Church History! What an amazing bravado we have when we are willing to denounce everyone and everywhere with only our private opinions alone! Is this not an amazingly twisted and negated Vincentian Canon? where our private interpretation trumps what (as St. Vincent of Lérins (400-50) famously said) has been "believed everywhere [ubique], always [semper], and by all [ab omnibus]!"
Karl Barth has also said, "So listen to my piece of advice: exegesis, exegesis, and yet more exegesis! Keep to the word, to the scripture that has been given to us." The human words in the Bible are a faithful and objective witness to the divine Word of God, but this is where we rely on the Church to explain the revelation of Jesus Christ to us, not as a deposit that may be used against all Church history, but that the Church may be a witness to the Word of God, and that the Church may constantly be revising its talk about God as it witnesses to the Word of God.
In the following quote, Karl Barth summarizes the positions of the famous Biblicist, Gottfried Menken, and demonstrates in his criticism that Menken has emulated the Enlightenment principles that Menken desired to oppose. The moral is, don't be a Biblicist!
An interesting peripheral phenomenon of Neo-Protestantism is the peculiar behaviour of the go-called Biblicism whose existence and character are strikingly presented in Gottfried Menken (1768-1831) of Bremen, writer who has never received sufficient notice in dogmatic history. Even in youth the characteristic complaint was made against Menken that it was "his obsession to try to construct Christianity out of the Bible alone " (Gildemeister, Leben und Werke des Dr. G. Menken, 1861, II. 7). That is the more or less explicit programme of this modern Biblicism.
"My reading is very limited yet very extended; it begins with Moses and ends with John. The Bible and the Bible alone I read and study" (ib. I, p. 21). He is not concerned with "what is old or new, with defending or attacking, with assent to the doctrine of any ecclesiastical party, with orthodoxy or heterodoxy, but only with the pure and genuine teaching of the Bible" (Schriften, 1858 f. VII, p. 256). And the Church? Menken prefers to avoid the word. For him and for all modern Biblicists it is a question of "Christianity, "reality" the "truth," the "kingdom of God." The Church is "the eternally pure possessor and preserver of the divine." Yet only too often its doctrine has "come under the influence of a passing philosophy or the superstitiously venerated theology of the fathers" (Schriften VII, p. 264). "In any case, where is the Church? Is it in the East or the West? Does it gather under the staff of the ecumenical Patriarch in Constantinople or under the threefold crown of the Pope at Rome? Finding no rest or portion in the world, did it long ago retire with the ancient Syrian Christians into the heart of Southern India or with the Waldenses into the valleys of Piedmont? In the fellowship of the Holy Ghost did it infallibly and irrevocably express itself at the Diet of Augsburg or at the Council of Trent or at the National Synod of Dort? Or finally is the true and perfect idea of Christian truth and doctrine to be found in the Idea fidei Fratrum? These few questions point to many things and embrace a large part of Christianity; but many different events, and systems and confessions and millions of Christians are outside their scope: Nestorians, Monophysite, Mennonites, Arminian, Jansenists, Mystics and Quakers; and many others, who all make claim to the name of the Christian Church and the treasure of Christian orthodoxy. These few questions are enough to show that, if we are not ignorant, or if after the customary manner and usage of sectarianism which becomes almost second nature, when we use the word Church we do not regard the confession of the Fathers and the sum total of those who agree with it as the only Christian fellowship in which true doctrine is to be found and to which alone, therefore. or primarily the name of Church belongs, it is not easy even to know what the Church believes and teaches. At an informative glance at so many different periods, countries, languages, systems, costumes and customs, at the confusion and tumult of so many different and contradictory warring sects, at the medley of so many different confessions and catechisms, it seems difficult and almost impossible to find a standpoint where with insight and teaches" (Schriften VII, p. 238). In these circumstances how can the Church have authority? "What is offered me as old is honoured by you as such only because it is found in a 16th-century catechism from the Palatinate or Saxony, or because an 11th-century Archbishop of Canterbury or a 5th-century Bishop of Hippo thought in this way and formulated and determined the matter accordingly. But if you could add to these human authorities a greater one in the utterances of a 2nd-century Bishop of Lyons. which you cannot, it would not make any material difference. For it does not matter to me to learn how Ursin or Luther or Anselm or Augustine or Irenaeus thought about the matter and formulated and determined it—they and their decisions are too new. I want that which is old, original and solely authentic: Holy Scripture itself " (Schriften, VII, p. 263f).
If these statements and arguments had been handed down without name or context, we might suppose that their author was of the Enlightenment instead of the passionate opponent of the Enlightenment which Menken actually was. And we find a similar agreement with Neo-Protestant anti-confessionalism in the later writer J. T. Beck, and partly too in Hofmann of Erlangen, and occasionally even in A. Schlatter. What does this agreement mean? We obviously have to ask whether here the Bible individually read and autonomously understood and expounded is not set up with the same sovereignty as others have exalted reason or feeling or experience or history as the one principle of theology? In this context does not the special treatment of the Bible—to the extent that it does not come under the relativism with which the Church is considered—take on something of self-glorification? Are we not dealing with a pious, but in its audacity no less explicitly modern leap into direct immediacy, with a laying hold of revelation, which, involving as it does a jettisoning of the fathers, although it purports to be a laying hold of the Bible, is perhaps something very different from the obedience of faith which only occurs when revelation lays hold of us by the word of the Bible? By nature is this absolutism of the Bible any different from that other absolutism which constituted decisive characteristic of the spirit and system of the 18th century as it culminated in the Enlightenment? And can it be very different in its consequences? Will those who will have the Bible alone as their master, as though Church history began again with them, really refrain from mastering the Bible? In the vacuum of their own seeking which this involves, will they perhaps hear Scripture better than in the sphere of the Church? In actual fact, there has never been a Biblicist who for all his grandiloquent appeal directly to Scripture against the fathers and tradition has proved himself so independent of the spirit and philosophy of his age and especially of his favourite religious ideas that in his teaching he has really allowed the Bible and the Bible alone to speak reliably by means or in spite of his anti-traditionalism. On the contrary, in the very Neo-Protestant peculiarities which we ﬁnd at crucial points especially in Menken but also in J. T. Beck. we are instructed that it is not advisable for serious students of Scripture so blithely to ignore the 16th century catechisms of the Palatinate and Saxony, or that 5th century Bishop of Hippo, or to refuse the guidance and correction afforded by the existence of Church fathers, as that biblicist programme involves. Otherwise there may be too easy and close an approximation to all kinds of other modern Titanisms. The Biblicism of the Reformers, as distinct from modern Biblicism, did not make this approximation because not in spite but in application of the Evangelical Scripture principle it kept itself free from this anti-traditionalism. J. A. Bengel, whose name is often mentioned in this context, showed at this point much greater wisdom than his more recent followers. Of course, we must not ignore but properly respect the fact that this modern Biblicism did ﬁnd itself in a relative opposition to Neo-Protestantism generally. It did give a necessary reminder of the Evangelical Scripture principle and in its own way it made an effective modern application of it at a crucial period. By way of it some important and true exegetical discoveries were made, and its outstanding representatives had a great personal dignity. But again that cannot prevent us from deﬁnitely rejecting its procedure in relation to the fathers as a basically liberal undertaking, just as we reject the thoughtlessness and lack of respect shown by all Neo-Protestantism in this regard.
Karl Barth, Church Dogmatics, Vol. 1.2, Sections 19-21: The Doctrine of The Word of God, Study Edition 5, pg 607-609