Hermeneutics 101 Failure

"The reader and student of the Bible must first understand the content of the New Testament writings in terms of how those in the first century would have understood it." - Gary DeMar, defending full preterism.

The primary and crucial principle, according to full preterists such as Gary DeMar, is actually a fundamental lapse in understanding the basic principles of hermeneutics.

Consider the following:

Mark 4 - And when he was alone, those around him with the twelve asked him about the parables....And he said to them, “Do you not understand this parable? How then will you understand all the parables?

Mark 13 - Then he left the crowds and went into the house. And his disciples came to him, saying, “Explain to us the parable of the weeds of the field.”

Matthew 15 - But Peter said to him, “Explain the parable to us.” And he said, “Are you also still without understanding? Do you not see that whatever goes into the mouth passes into the stomach and is expelled?

Matthew 16 - When the disciples reached the other side, they had forgotten to bring any bread. Jesus said to them, “Watch and beware of the leaven of the Pharisees and Sadducees.” And they began discussing it among themselves, saying, “We brought no bread.” But Jesus, aware of this, said, “O you of little faith, why are you discussing among yourselves the fact that you have no bread? Do you not yet perceive? Do you not remember the five loaves for the five thousand, and how many baskets you gathered?

Mark 9 - They went on from there and passed through Galilee. And he did not want anyone to know, for he was teaching his disciples, saying to them, “The Son of Man is going to be delivered into the hands of men, and they will kill him. And when he is killed, after three days he will rise.” But they did not understand the saying, and were afraid to ask him.

Matthew 27 - And about the ninth hour Jesus cried out with a loud voice, saying, “Eli, Eli, lema sabachthani?” that is, “My God, my God, why have you forsaken me?” And some of the bystanders, hearing it, said, “This man is calling Elijah.

Luke 24 - While they were talking and discussing together, Jesus himself drew near and went with them. But their eyes were kept from recognizing him.

John 20 - Jesus said to her, “Woman, why are you weeping? Whom are you seeking?” Supposing him to be the gardener, she said to him, “Sir, if you have carried him away, tell me where you have laid him, and I will take him away.”

John 21 - Just as day was breaking, Jesus stood on the shore; yet the disciples did not know that it was Jesus.

John 21 - So the saying spread abroad among the brothers that this disciple was not to die; yet Jesus did not say to him that he was not to die, but, “If it is my will that he remain until I come, what is that to you?”
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I could point out more, but I think you get the point. It is NOT our task to "first understand the content of the New Testament writings in terms of how those in the first century would have understood it."

It is our task to understand what the original author intended. The original audience oftentimes got it wrong, just as the full preterists get it wrong.