Jephthah knows about God, and his knowledge about God is correct, but Jephthah doesn't know God! Think of this! He is facing the greatest crisis of his life, and he doesn't know God! He only knows about Him.

Jesus was quick to give the credit to God. Although He was God Himself... He quickly and reflexively gave the credit for virtue to His heavenly Father. It is this set of heart and mind that avoids the pride of life and lives in humble reliance upon God.