I recently wrote this to a friend who was exploring the idea that Jesus manifested in the Old Testament as well as the new. It is largely the first chapter of the Book of John that makes this assertion. I think it is an interesting subject, so I bring my response here for anyone to read who might be interested. I believe the book of John spells out in his first chapter just what 'Jesus' is, and the conceptual relationship between 'Jesus' and 'God.' I think that you are right if you believe that, in a certain respect, 'Jesus' manifested in the Old Testament. You seem to say that, but stop short of stating in boldfaced. According to John, John 1 1In the beginning was the Word, and the Word was with God, and the Word was God. 2The same was in the beginning with God. 3All things were made by him; and without him was not any thing made that was made. 4In him was life; and the life was the light of men. 5And the light shineth in darkness; and the darkness comprehended it not. I believe a key term here is "Word." God's Word, just like our word, is God's expression of His intentions. But John tells us that God's 'Word' is more than that. John tells us that God's Word is also the means for carrying out those intentions. God 'spoke' the world into existence. So God needs only to express His Word, His intention to create, and creation occurs. So God's Word is both God's intentions and the means to execute those intentions. Verse 1 tells us that God's intentions, and the means of carrying out those intentions, have always been a part of all-powerful God. But we also know that God has no beginning, and no end, a beginning to which verse 2 alludes. So verse 2 cannot refer to a beginning of God Himself, Who, as Spirit, has always existed within a spirit world, a world that has no beginning, and no end. The term 'beginning' therefore can only refer to this natural world, in parallel meaning to Genesis 1, the story of the natural world creation, which world plainly did have a beginning, and is foretold in the scriptures to have an end. So in the beginning of the natural world were certain intentions of God to create this same world, together with the means of carrying out those intentions. So God, Who John later tells us is Spirit, living in a spirit world, had to have a natural world interface, or perhaps manifestation, to carry out the intentions of all that He intended for this natural world. Verse 1 tells us that this 'interface,' has always been a part of God, being 'with' God, and being ('was') God. But until the natural world was to be made, and was made, that aspect of God which created the natural world was not manifest. Only as the Spirit of God moved to create the natural world did this natural world 'interface' manifest. This natural world manifestation of God could not have existed prior to the natural world, except in the form of pure potential. That is because for this potential to manifest, the natural world had to exist. Otherwise this facet of God had nothing to interface with. So God spoke the Word, expressing His intention that the natural world should come into being, and in doing so, that simultaneously injected the existence of the Word, God's overall intentions for such a world, and the means to carry out those intentions, into the natural world. And it is that aspect of God, which according to John, 'made all that was made.' 14And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth. And God's intentions, and the means to carry out those intentions, eventually became flesh, taking on human form dwelling among us. But Jesus was more than a man, and God. Jesus was, and is, the means, a tool, toward God's ultimate goal of reconciling men with Himself, to live forever and together in God's Kingdom. So rather than simply being human and God simultaneously, I believe that Jesus can be thought of more as God's chosen means to His ultimate ends. Perhaps there have been other means that God could have and did utilize, for example the burning bush or the angel of the Lord. But these passages tell us that Jesus is a natural world embodiment of the means to achieve God's ultimate goal, a natural world manifestation of God's intentions, and the means to carry out those intentions, AKA, God's Word. So whenever and wherever in the Old Testament that God manifests, Angel of the Lord perhaps, burning bush perhaps, that manifestation is part and parcel of the same Word of God injected into the natural world at creation, that aspect of God that did the creating, the purpose of which was, and is, to carry out God's intentions. That Word ultimately became flesh, born of a virgin, Jesus Christ, Who along with fulfilling all of God's other intentions for the natural world, also serves the purpose of reconciling imperfect man, with perfect God. Until Jesus Christ presented in the natural world, there was no path or manner in the natural world for God to carry out that purpose. As John the Baptist said, Jesus is the Lamb of God Who came into the world to subsequently leave and take sin out of the world, thus reconciling God and man.