I believe for the most part that Christianity had its origins in a series of visions. These visions, I believe, were naturally-caused and are in no need of supernatural/divine causation. Many Christians will object by saying that while individuals may have hallucinations or visions, it cannot happen to a group or collection of people at the same time. This, I believe, is wrong. What I wish to show in this post is 1.) that visions have occured in antiquity, 2.) that they occur to groups of people at a time, and 3.) they were so common in antiquity that they were considered actually to be normal.
To accomplish these three goals, I wish to provide the social-scientific basis for such visions. Then, I wish to give a few examples of what I consider to be these kinds of visions in history. Let me start with the social-scientific basis of the visions that I have in mind.In pages 327-329 of their excellent Social Science Commentary on the Synoptic Gospels, Bruce Malina and Richard Rohrbaugh engage in a discussion on "Altered-States-of-Conciousness". I reproduce their section below:"Anthropologists studying cross-cultural psychology define altered states of conciousness as conditions in which sensations, perceptions, cognition, and emotions are altered. Such states are characterized by changes in sensing, perceiving, thinking, and feeling. When a person is in such a state, the experience modifies the relatoin of the individual to the self, body, sense of identity, and the enviroment of time, space, or other people. One scholar has identified twenty such states of conciousness: dreaming, hynogogic (drowsiness before sleep), hypnopompic (semiconsciousness preceding waking), hyperalert, lethargic, rapture, hysteric, fragmentation, regressive, meditative, trance, reverie, daydreaming, internal scanning, stupor, coma, sotred memory, expanded consciousness, and 'normal'. In trace or in any other altered state of conciousness, a visionary encounters, indeed enters, another level of aspect of reality registered physiologically in the brain in the same way 'normal' experiences are. Culturally 'normal' of consensual reality is that aspect of dimension of reality of which a person is most commonly aware most of the time."Alternate reality describes that dimension of reality in which the deity and spirits reside, in which human beings from culturally 'normal' reality can sometimes visit in ecstatic trance by taking a journey (variously called "sky journey" or "soul loss" and the like), and to which people go when they die (Those who do not believe any of these things would call this nonconsensual reality.) During the centuries before and after the Gospels were written, countless persons reported a range of visions and appearances involving celestial entities. There is no reason not to take the experiences of these persons seriously, at their word. Their experiences have to be interpreted within the framework of their own culture's consensus reality (rather than ours)."The authors go onto list five main incidents of these kinds of visions and appearances; the baptism of Jesus, the testing of Jesus, the miracle of walking on the sea, the Transfiguration, and the Resurrection appearances. Their comments on the resurrection appearances are especially pertinent. They say:"The appearances of Jesus raised by God are visions of Jesus in alternate reality, where he, as God's chosen holy one, continues to live. The appearances of a holy man are altered-states-of-conciousness experiences and therefore are quite real. The interpretation that the disciples gave to these experiences was that God had raised Jesus from the dead. Mainstream U.S. culture frowns upon and even denies the human capacity for visions, trances, and experiencs of alternate realities. We are very cruious about nonrational dimensions of human existence, but tend to label all such occurences as irrational. John Pilch cites the work of Erika Bourguignon, who compiled a sample of 488 societies in all parts of the world, at various levels of technological complexity, and found that ninety percent of these societies evidence 'altered states of conciousness' Her conclusion: "Societies which do not utilize these states are historical exceptions which need to be explained, rather than the vast majority of societies that do not use these states" (cited by Pilch 1993). Thus it would be quite anachronistic and ethnocentric to take our post-Enlightenment, post-industrial revolution, technologically obsessed society as the normative for judging anyone other than ourselves. For most of the world, even today, a report of altered states of awareness would be considered quite normal."Cross-cultural comparison suggests that the Gospel authors describe experiences of altered states of awareness. This may be difficult for us to believe because we have been enculturated to be selectively inattentive to such states of awareness except in dreamsand under the influence of controlled substances."I have highlighted in bold what I consider to be important points relative to my arguments. First of all, note that Malina and Rohrbaugh consider the postmortem appearances of Jesus to be "visions". Note also, that they point out that visions of a holy man are in altered-states-of-awareness. Next, note that during the time before and after the Gospels were written that these visions and appearancs were widely reported in history and that they involved altered-states-of-consciousness. Finally note that the U.S. appears to be the exception, not the norm, and that these kinds of ASC type of visions are normative and considered usual in honor-shame soceities. This provides, I believe, the social-scientific basis for visions. Now as for specific examples of these kinds of visions in history involving ASC.
My first example is from Gershom Scholem's remarks on "the messianic revival of Sabbatai Sevi": The people of Smyrna saw miracles and heard prophecies, providing the best possible illustration of Renan's remark about the infectious character of visions. It is enough for one member of a group sharing the same beliefs to claim to have seen or heard a supernatural manifestation, and the others too will see and hear it. Hardly had the report arrived from Aleppo that Elijah had appeared in the Old Synagogue there, and Elijah walked the streets of Smyrna. Dozens, even hundreds, had seen him.... A letter written in Constantinople notes apparitions of Elijah "whom many have seen." In fact, visions of Sevi were very common after his death to his followers from what I understand (Price, Beyond Born Again, "Guarding an Empty Tomb"). These visions of Sevi can be understood as having occured in altered-states-of-consciousness, just like what Malina and Rohrbaugh have argued. Robin Lane Fox, in his work Pagans and Christians also seems to provide an example of a ASC- group vision:"Every visitor to the Black Sea knew the special island of Achilles, and in his report on the area, a visiting governor, Arrian, informed the Emperor Hadrian how 'some said' Achilles appeared to them in broad daylight on the prow or mast of their ships, 'as did Castor and Pollux'. Maximus, indeed knew a man after Homer's own heart. Near the same island, visitors had 'often' seen a young, fair-haired hero dancing in armour and had heard him singing a paean." (Fox pg. 144).According to Fox, Arrian informed Emperor Hadrian of reports that Achilles had appeared to groups of visitors to that special island of Achilles. In fact, according to this report, visitors "had often seen" what they took to be Achilles. In fact, Fox stresses that Miletus was alive with glimpses of the gods which had been granted to all sorts of people (pg. 143). Granted, Achilles and Sevi were probably not in the least considered holy men, but that's not my point here; rather my point is that these kinds of group visions involving altered-states-of-consciousness were common in antiquity. In fact, one can argue that legends arose from these kinds of visions. Even if some stories of these kinds of visions are pure legends, one can reasonably argue that the legends might reflect actual visionary experiences of these kinds.
This, I consider to be the naturalistic basis upon which Christianity was founded on.