I very much appreciate my guest's comments of the past few days, but it appears that we differ in our interpretation of the history of this subject. As my previous posts here have indicated, I did participate in Dr. Jacob Wright's online course (and enjoyed it very much). Like my guest, I do not share all of Dr. Wright's conclusions about the Bible; but I do find his general thesis (see my second rationale in yesterday's post) to be a compelling and plausible explanation of both the archeological and historical evidence available to us.
To be sure, my guest is in good company in the role that he/she assigns to Constantine in this matter; but I believe that the emperor's role in this story is more complex and nuanced than many students of this history have imagined. Perhaps I am more sensitive to this subject because of my background in a religious culture (Worldwide Church of God) that twisted their account of Constantine's role relative to the evolution of the Christian religion. In short, they interpreted his actions and decrees to justify some of their own beliefs/teachings (e.g. they claimed that he changed the Christian day of worship from the Sabbath to Sunday - which is not true, but that's another story).
Emperor Constantine was a brilliant visionary and a political opportunist. Although it would be presumptuous of us to attempt to judge what was in a man's heart that lived so many centuries ago, we do know that the evidence of his life's work underscores two primary objectives of the emperor: 1) to consolidate and centralize power within himself, and 2) to rebuild and strengthen the Roman Empire. It is not important for us to know whether or not the Emperor's vision of a cross before his battle with Maxentius actually happened or if it prompted a sincere change of heart (or some kind of religious conversion) on the part of Constantine. It does mesh, however, with the political objectives mentioned above. The fact that the emperor attributed his political ascendancy over his adversaries to this vision tells us volumes about the strength of the Christian community within the empire.
Many Roman historians have described the attitude of the imperial government (along with most of the citizenry) toward religion as being almost laissez faire in nature. In other words, as long as one's personal beliefs and religious practices did not interfere with one's obligations to the state, most folks simply did not care what you believed or practiced. In fact, it is clear that Augustus and his successors regarded the public expression of religion as a tool of the state - something to promote cohesion and unity (as in worship of the Emperor). Hence, the persecution of Christianity within the empire was in large part a reaction to a perception that this group undermined the emperor's authority and threatened the peace, cohesion and unity of the empire. In other words, they were a troublesome minority that needed to be stamped out.
Nevertheless, even in the face of determined persecution, the cult of the Christian religion had grown in numbers and had spread throughout much of the territory of the Roman Empire by the time of Constantine. In his quest for imperial supremacy, Constantine sought to associate himself with what had by that time been adopted as the religion of a large number of his subjects. Thus the emperor embraced the cross because it was so widely regarded as the principal symbol of the Christians. He declared Sunday as an official day of rest because it was the day on which a majority of his subjects (Christian and Pagan) had chosen to worship their god(s). Once again, whatever his personal beliefs, the emperor needed a peaceful, cohesive and unified realm to govern.
Although there was apparently some degree of consensus among Christians by the Fourth Century about which texts/writings of the early church were authoritative, there had never been anything like an official canon of sacred writings for the community. To remedy this situation and forestall quarrelling and dissension within their ranks, Constantine quite purposefully gathered together some of the leading voices within the Christian community and enjoined them to reach agreement over which of the ancient texts/writings would be regarded as their standard. After all, if he was going to recognize these people as a legitimate religion within his state, he felt that he had the right to demand that they be united and at peace with each other (Constantine never made Christianity the state religion - that happened later under Emperor Theodosius). Hence, it is misleading to say that the emperor was personally responsible for the Christian canon (Indeed, it is generally agreed that the emperor did not appear to be very interested in which texts were included - his objective was clearly unity). Although his role in the evolution of that canon was clearly important by anyone's standard, it was not the determinative one that many have attributed to him.
What is the point of this little history lesson? It is inaccurate to assign the Emperor Constantine with responsibility for the spread and popularity of the Christian religion. It is also inconsistent with the facts to give him credit for the Christian canon or the introduction of the Hebrew Scriptures to the Western World. I would describe all of these developments as evolutionary in nature and happening over many centuries, but I would say that Jesus Christ and his disciples were the most important factors in introducing the Western World to these concepts and promoting their acceptance. To be sure, the emperor is an important part of this history; but his role was much more nuanced than both many Christians and Atheists have been willing to admit (agendas are very dangerous to an objective account of history).