"In the beginning God created the heavens and the earth" (Genesis 1:1).
Biblical creation is the most important basic assumption in Christian theory of knowledge. Only faith in God and His word will cause someone to accept this basic assumption.
Note: This is the devotional summary of my lecture in Genesis delivered at the Presbyterian Theological Seminary, Philippines. The lecture is based on Chapter 1 of Gary North's economic commentary on Genesis, pages 8-20. You can read the original content of the lecture here.