What are higher and lower criticism?

What is historical criticism (also known as higher criticism)? What is textual criticism (also known as lower criticism)? How can they help us understand the scriptures? How can they interefere with our understanding of the scriptures?

---

Jesus told us the source of his teaching:

   Joh 14:24 ... and the word which ye hear is not mine, but the Father’s which sent me.

The Old Testament is the word of God, and Jesus "spoke the dark sayings of old."

And he told his disciples to teach others the same thing:

   Mt 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, [even] unto the end of the world. Amen.

He said that the Holy Ghost would remind them of everything he taught them:

   Joh 14:26 But the Comforter, [which is] the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.

Since the source of the New Testament is made clear by the New Testament itself, higher and lower criticism imterfere with our understanding of scripture by throwing doubt on God's word. Sensus plenior presumes that the source of Jesus's knowledge of himself is the Old Testament, and an active dialog with the father through "dinner theater" similar to those of the prophets. As such it is a type of source criticism based in faith rather than disbelief.

Jesus saw a prophecy that when he was 12 he was to "rebel" and so he stayed in the temple to teach as a way of rebelling without sin. The story of the 9 kings of Chedloamer was his source. He could say, "I only do what I see the Father doing in the scriptures".