Very often, people misread the term "total truth" to mean absolute or worse, totalizing truth. When Schaeffer used the term, he meant something like "comprehensive, all encompassing" truth, meaning we dun put religion in a box and say it is true in my heart, but is irrelevant when it comes to other areas of life ie ethics, business, science, governance etc
In Nancy Pearcey's context, she is writing to encourage christians to engage a secular society that seeks to weed out the sacred... In our context, we have a different issue where religion and the state are too close (not too separate) so much so tat politicians exploit religion for personal gain and religion uses politics to curtail differing views...
Can a Christian support a qualified secular state and remain consistent in our belief that the Christian faith is a comprehensive way of life? I believe so, provided we are clear on what that means.
Kam Weng posted a helpful way of framing the issue here
"The qualified-secular status of the Malaysian Federal Constitution is been challenged in current debates on religion and society. Some Muslim activists reject the provision for the separation between state and religion since it does not grant due recognition to Islam as the religion of the majority. It is granted that religion (this includes all religions and not just Islam) is an integrated worldview and way of life. As such, practicing religion entails engagement with social life. It is futile, if not wrong to dichotomize these two spheres of human activities.
When we talk about separation between Church/Mosque and State, we are not suggesting a dichotomy between religion and society as spheres of human activity. We are suggesting the need to separate religious institutions from state institutions. We are calling for institutional separation. The separation is necessary both to protect state authorities from exploiting religion for their own political agenda and to prevent religious authorities from exploiting the state apparatus for their own (sectarian) religious agenda."