Biblicism is the view that Scripture is the only reliable source of knowledge. It is often expressed as a rejection of other sources of knowledge, as here, by Henry Morris,
the direct [written] testimony from the Creator [is] the only way to know the age of the earth.Morris, one of the fathers of "creation science" and young-earth creationism (as co-author of The Genesis Flood, released in 1961), seems blissfully unaware that science has historically helped to correct the church's misinterpretations of Scripture. It was the knowledge provided by astronomy that eventually led to acceptance of heliocentrism (though I understand there are still a few biblicist holdouts even on that one). And, of course, Christians used to believe that Scripture taught a flat Earth, and it was knowledge outside the Bible that helped correct that wrong interpretation as well. So there are clear historical examples that serve to refute such biblicism.
But more fundamentally, biblicism is self-refuting, or self-referentially absurd. I've addressed this problem before, generally as regards other flawed theories about knowledge, such as scientism, empiricism, or postmodern epistemological claims. A self-refuting statement is one that disqualifies itself, a truth claim that, when applied to itself, renders itself false. So, for example, scientism,
The only reliable knowledge is that which results from scientific testingis self-refuting because there is no scientific test or set of tests that could be performed to yield that knowledge (the knowledge that only scientifically-derived knowledge is reliable).
Likewise, the postmodern claim that
There are no universal truthspresents itself as a universal truth. If I believed it, that would be reason to reject all universal truths, including that one.
Biblicism suffers the same problem. It has this in common with scientism and empiricism: each is a self-serving attempt to limit the range of knowledge to exclude other sources. All such artificial epistemologies will be self-refuting.
The biblicism of Morris, Ken Ham, and others is self-refuting in at least two ways.
First, the Bible itself never makes this claim. Rather, Scripture appeals throughout to other sources of knowledge, calling people to observe the created order for knowledge about God. In fact, according to Romans 1:18-21, all men have knowledge of God that comes from the creation (not Scripture) and it is rejection of this knowledge that is sufficient to condemn them.
Second, one simply must bring an entire set of knowledge to the task of understanding Scripture. The Bible does not teach the meaning of the words and grammar it uses (in Hebrew, Greek, or even English); instead, we must have such knowledge beforehand. Likewise, Scripture does not itself teach the laws of logic; rather it assumes them on every page. It is because we understand--by knowledge derived outside of Scripture--the law of non-contradiction that we are able to affirm that when Jesus said "No one comes to the Father but by me" He did not simultaneously mean "Many people come to the Father through other means."
The biblicist claim is thus seen to be almost incredibly naive and simplistic.
To the question, "How do we know there is a God?" the historical Christian answer has been "Because God has revealed Himself to us, and that both through the creation itself and through divinely-inspired Scripture." This historical Christian doctrine of dual revelation was especially important to several of the early church fathers (see the Augustine quote in the post mentioned at the outset) and to the Protestant reformers. But young-earth creationists (like Answers in Genesis) reject this historical doctrine* because evidence from astronomy, geology, physics, and such overwhelmingly refutes their superficial interpretation of Genesis.
*In addition to rejecting the historical doctrine of dual revelation, biblicists grossly distort another doctrine important to the Reformers, that of Sola Scriptura. This doctrine did not distinguish between Scripture and other God-given sources of knowledge. Instead, it elevated Scripture over church tradition, where the latter was (and is) seen as equally important by Roman Catholicism. Despite attempts by young-earth creationists to link their biblicism to Sola Scriptura, the Protestant Reformers would have found biblicism as unbiblical and illogical as I do.