The Gospels are Scripture, Heb. 2:3 The writings of the Apostles are Scripture, 1 Cor. 2:7-13, 1 Pet. 1:12, 2 Pet. 3:1-2, 15-16, Rev. is Scripture, Rev. 1:2 Then of course we have 2 Tim. 3:16, 2 Pet.1:21.
So, if I understand you correctly, you are saying that you know that the Christian scriptures are inspired by God because the very scriptures themselves assert divine inspiration?