Van Til: Common grace, ultimate and proximate starting points and arithmetic

I'm currently reading some essays Van Til wrote on the foundations of Christian education and came across this nugget where Van Til mentions how common grace interacts with ultimate and proximate starting points:

"Common grace points specifically to the fact that similarities between the people of God and the people of this world are but proximate similarities and that these proximate similarities play before the background of ultimate differences. If people do not believe in common grace or do not know what it means, they are likely to raise proximate similarities to ultimate similarities or to raise proximate differences to ultimate differences with the result that the absolute differences are toned down. It is this which has often taken place in non-Reformed churches.

There it has been thought that religion is a condiment that may be added to the otherwise neutral territories of life. Because they knew not the doctrine of common grace they took it for granted that no ultimate difference could be hidden behind the statement of a Christian that two times two are four and a statement of a non-Christian that two times two are four.

Now the fact that two times two are four does not mean the same thing to you as a believer and to someone else as an unbeliever. When you think of two times two as four you connect this fact with numerical law. And when you connect this fact with numerical law you must connect numerical law with all law. The question you face then is whether any law exists in its own right or is an expression of the will and nature of God.

Thus the fact that two times two are four enables you to implicate yourself more deeply into the nature and will of God. On the other hand, when an unbeliever says that two times two are four he will also be led to connect this fact with the whole idea of law but will regard this law as independent of God. Thus the fact that two times two are four enables him to get farther away from God.

That fact will place the unbeliever before a whole sea of open possibilities in which he may seek to realize his life away from God. And it is this basic difference between what two times two are four means to the believer and what it means to the unbeliever that the doctrine of common grace has helped us to see. It has enabled us to focus our attention on the antithesis without fearing that we are doing injustice to any of the facts that surround us."

- Cornelius Van Til, Foundations of Christian education

I would highly recommend people acquire this book for their library if they haven't done so yet. Van Til offers a very clear summary of his apologetics and lays the foundation that can assist in raising and educating the next generation of Christians.