A problem with presuppositional apologetics

Presuppositional apologetics, as advocated by Cornelius Van Til is popular in some circles. Although there are certain sentiments behind it that I have sympathy with, it can be quite problematic, particularly in practical application, and its attitude to secular scholarship.

The latest issue of Science and Christian Belief has a review of a recent book What the Heavens Declare: Science in the Light of Creation by Lydia Jaeger.
The reviewer, William Simpson, has the following valuable insight.

Unfortunately the presuppositional school persistently confuses the ‘order of knowing’ with the ‘order of being’: from the insistence that God is ‘the foundation of everything that exists’, it simply does not follow that we must begin with God’s existence in order to explain anything. 

For example: in the order of being, the university town of St Andrews precedes any road sign that points to it; the one, presumably, would not be present without the other. In the order of knowing, however, the road signs may precede the town for a traveller trying to find his way to it. The theological twist behind the epistemic slip is more serious: in Calvin’s nomenclature, it involves an unbiblical refusal to seek common ground, grounded in common grace, with non-Christians.