Think of the bible like a 1000 piece picture puzzle. The information recorded in various books of the bible was written down gradually over 1600 years. The first books of the bible only revealed small details about Gods purpose, other prophets slowly added more information and finally Christ revealed the final pieces of the puzzle needed to see the complete picture.
With a complete picture, there are no more pieces of the puzzle needed. Its complete. We know this because those final pieces of the puzzle show us the final outcome of Gods purpose and plan therefore he has given us all the information we need...for now.
You see Pegg I have a very big problem with that idea - that God revealed less to previous ages than He did in later ages. Logically this would not make any sense. Let me explain
Christ said "I am the way the truth and the life;
no one comes unto the Father but by me". Now if you believe that statement - which you must as a Christian - then it means that no one can be saved unless they have faith in Jesus Christ. Now Jesus, when relating the story of the rich man and Lazarus, implied that he believed Abraham was saved. But, according to Jesus, Abraham could only be saved if he believed in Jesus Christ. Therefore it means Abraham had the Gospel of Jesus Christ just as we have it today.
Again Jesus said "Except a man be born of water and of the spirit
he can in nowise enter into the kingdom of heaven". And Christ proved the importance of his words by his own baptism. He was sinless yet he was baptism and he did not receive the gift of the Holy Ghost until after He was baptized. And God the Father declared it his baptism that he was pleased. Now if Christ, the sinless Son of God, could not escape the commandment to be baptised and receive the Holy Ghost then how could Adam, Moses, Abraham, Noah, Enoch, Seth, Melchizedek, Isaiah Isaac, Jacob or anyone else have escaped it? How could they have been exempt when the Son of God was not?
And if they were not exempt then that means God must have taught them the same Gospel he sent Jesus to preach. And if they were taught the same Gospel then what new thing did Jesus preach? Jesus taught nothing new. God is not a learning God. He doesn't get more intelligent over time. He is the same yesterday, today and forever. His knowledge is and always was perfect and complete. Therefore his plan to save the human race has always been the same.
From the time Adam fell God always intended to save mankind by sending his Son. And this he made known to the ancient people who believed in him. And hence we have in John 8:56 Jesus saying "Your father Abraham rejoiced to see my day: and he saw it, and was glad." The ancient new about Jesus, what he would do and say. Therefore when Jesus came and spoke and worked miracles, he was only fulfilling the prophecies that had already been made: it was nothing new.
So then, if Christ brought nothing new with his coming, how then can we say that his coming justifies the closing of the canon. Especially since the canon did not stop at his coming. It continued with Apostles and Prophets after him. And there is absolutely no indication that when John said no one must add or subtract to the words of "this scroll" that he meant anything other that "the Book of Revelation" since the Bible had not even been compiled.