It seems to me that scholars use this phrase to indicate the group that coalesced around the personality, teachings, and legends of Jesus before the group can be properly called "Christianity." It also occurs to me that using sociological language for this group allows us to avoid talk of messianism, experiences of divine intervention, and other god-talk and thus avoid the appearance of religion. I.e. social-scientific language sanitizes Jesus for secular consumption. Or maybe it's just that biblical studies (alongside the rest of the humanities) has been trying to appear more like the "hard sciences" in the era of modernity. Whatever the case, somewhere along the way we adopted this particular sociological category: "movement."
But it must be asked: was the Jesus movement a "movement"?
In my research, "social movements" are variously defined by sociologists. But, in general terms, successful movements tend to have a few discernible features:
1. A deeply felt social problem. This must be a specifically named experience of shared suffering or social discontentment. I.e. there must be an impetus for a social antidote around which the social movement rallies.By this short gloss of a framework, was the Jesus movement a social movement? I think not. But I am willing to be convinced otherwise. Do please chime in to help me.
2. A charismatic personality. This is "charisma" in Weber's sense. I.e. we're not talking about a gregarious fellow necessarily. We not talking about gifts of the spirit necessarily. Rather, this personality is seen as exceptional in some way. He or she may be a gifted orator or may perform amazing actions that inspire social change. This person usually communicates a direction for the group and accesses resources that mobilize them. This person tends to be an authoritarian, acting unilaterally and forcefully commanding his/her following. This person attempts to revolutionize or reform a particular status quo.
3. A shared ideology: The group must be motivated by a sense of shared moral judgements, intentions, and symbols by which they orient their lives.
4. Organization: The leader(s) must be able to marshal economic, political, cultural, and/or military resources to make the movement move.
There is no doubt that Jesus' following identified social problems. But does any single social problem explain the emergence of the collective identity? I suppose anti-Rome folks will point to Roman colonization and domination as the key. After all, "kingdom (or rule) of God" probably stands in opposition to Roman rule. But does this motivation explain why Jesus' following, teachings, charismatic actions, etc. took the specific shape that they took? Probably not.
The second stage (and it should be said that stages 2, 3, and 4 happen almost simultaneously most of the time) is the only stage that works for Jesus and his followers. Jesus was an exorcist and a healer. This might have been enough to draw crowds. He (or so it seems) was a skill orator. But then we run into number three....
The third stage is another dilemma. What was the shared ideology of Jesus' so-called "movement"? Eschatology? The belief that Israel's God would return as Judge? Care for the poor? Okay, fine. But how does this differ from many (most?) groups within the Second Temple period? Moreover, Jesus' stories and puzzling sayings often confuse rather than clarify. We must wonder whether a specific ideology was being promoted. After all, early Christianity seems to branch out in several directions.
The fourth stage is also a dilemma. Jesus seems much more like an unpredictable holy man who runs from crowds and much less like an authoritarian who organizes them into a force.
In order to call Jesus' following a "movement" we have to force Jesus into a sociological model that doesn't work. I am much more inclined to think of Jesus as a charismatic personality who ends up alienating most of his followers. It could be that early Christianity rallies around the problem of the Cross and thus launches a "social movement." But this doesn't explain how/why Jesus' initial following came together.
In short, the most important dilemma here is identifying the "social problem" (i.e. stage one). What is the specifically named experience of shared suffering or social discontentment? Sickness? Demons? Rome? Agrarian economic disparity? Differences of opinion on purity issues?