Putting God to the test

From Doug Kelly's newly released systematic theology volume 1:

From beginning to end, it must clearly be recognized that the only way humans can properly test truth claims to ultimate reality must be in the light of who that ultimate reality is and how He acts and speaks.

The supreme reality makes himself known as the personal God, and hence the supreme truth he reveals at its very heart partakes of His personal reality and is, for that reason, what the Greek Church Fathers call autousia (that is, 'self-existence' or 'self-evidence').

That is to say, the supreme truth of the personal God does not depend on anything outside itself to validate itself, for why should that which is ultimate be dependent on that which is subordinate for its power to convince?

Douglas F. Kelly, Systematic Theology Volume 1: The God Who Is: The Holy Trinity, p. 15

Why not order it for Christmas here or here.