Before we start on the adventure of determining how a Jewish rabbi became God, we need to establish the ground rules (our method and assumptions).
1. This is a critical venture, not an apologetic one. This is perhaps the most important ground rule we can put into place, and stick by at all costs. What the theologians back in the nineteenth and early twentieth centuries realized is that for the study of religion to be an academic enterprise comparable to the study of history or literature or the arts, it cannot be apologetic. If we want to understand how any religion comes into existence and grows, we cannot be invested in the promotion or rescue of that particular religion. We have to leave our own theological interests at the door.
2. We cannot grant special privileges to the religion we are studying. This means that we cannot allow for God to perform miracles when it is convenient for our explanations. We cannot suspend what we know to be scientifically true about our world and grant a religion special treatment or supernatural explanations. The critical study of religion is not about proving or defending one's own religious beliefs or the special claims of a particular religious community. It isn't about disproving them either. The critical study of religion does not amount to outsiders attacking what should not be attacked. It is about dealing fair and square with religion in an objective scientific manner using reason that relies on verifiable research, and not allowing for special knowledge of God, revelations, or privileges to be granted to the religion. For those people who want to use the post-modern avoidance strategy and argue that there is no objective truth but only pluralisms, well you need to go back and reread your philosophy and your science. Although the historical enterprise is recognizably subjective, this does not mean that it is unscientific or that it does not result in research that is as objective as possible.
3. We must suspend canonical thinking and boundaries. We must deal equitably with all of our ancient sources, having no preconceived judgments about them based on whether they are in or out of the bible, whether they support or deny traditional theological or christological formulations, and whether they were written by the winners or the losers in the battle over Christianity. There are no heretics or heretical literature, except in terms of how various historical groups may have perceived each other.
4. We begin with the assumption that Christianity did not fall out of the sky one day, but it originated on earth among human beings and developed in complex social, political, and religious environments.
5. The sources that have been left behind were written by human beings and reflect the complexity of the growth of Christianity.
6. Our sources are not neutral. They were not written to report objective factual history. They were written for a variety of reasons including apology and polemic and propaganda. They often reflect a communal interest, and thus do not necessarily tell us what happened but what the community wanted to happen, thought should happen, or wanted remembered about them.
7. Our sources are dependent on the human being, physiologically, psychologically, emotionally, socially. The stories they relate are the consequence of human experience and human memory which itself is a constructive process with many implications. Eyewitness testimony (even in those cases where we might have it in our sources) does not guarantee the "reliability" or "authenticity" of anything reported. Not only is intentional lying a possibility that we cannot simply set aside, but human memory (because it is a social constructive process) has been proven to distort. Social memory likewise.
With these ground rules in place, we will be ready to begin trying to figure out how Jesus became God.