From my Colson Center article ‘The Abstraction of God and the Culture Wars‘:
Creation expresses God’s nature; as such, the ordering of reality creates the context in which God’s commands can be seen as normative. Precisely because of this, we shouldn’t think that individuals or cultures without access to God’s explicit commands are completely bereft of ethical consciousness.
Though this may seem like a small point, this has profound ramifications for how we approach apologetics. For example, we should be filled with horror at the way Karl Barth (and many advocates of, so called “presuppositional apologetics” as well) taught that until an unbeliever explicitly presupposes the truth of Scripture that there is no point at which we can, or ought, to try to connect with them philosophically. Barth expressed this erroneous view in The Doctrine of the Word of God, when he declared that “Man’s capacity for God, however it may be with his humanity and personality, has really been lost. We cannot, therefore, see that at this point there comes into view a common basis of discussion for philosophical and theological anthropology, the opportunity for a common exhibition at least of the possibility of raising the question about God.”
In the later 20th century we saw a similar error in the attack against evidentialist apologetics that became trendy for Reformed theologians following Cornelius Van Til. In its worst forms, the rejection of evidentialism was often proffered on the spurious ground that one must first buy into the whole Christian package in order to make sense of anything. What is missed, or at least not given sufficient attention in this paradigm, is the fact that there are verities which believers and unbelievers share in common by virtue of our shared creation; verities that form a basis for discussion for philosophical and theological anthropology.