Often we hear words like "consensus," "majority," etc., thrown around, without stopping to think about them. What exactly do we mean by the words. They of course are purely heuristic, ways of describing the current state of play in the discipline. For whomever is interested, I thought I'd put out there what I mean when I such words.
Consensus: virtually all scholars in the field affirm a given proposition, to the point that the statement "Person X is a scholar in field Y" is virtually synonymous with the statement "Person X believes that Z is the case." In other words, the percentage of persons in the field holding this opinion is virtually 100%, statistically negligible numbers rejecting the opinion notwithstanding (in other words, the fact that two NT scholars have said they think Jesus did not exist does not obviate the fact that this is a consensus). That Jesus existed and was Jewish is an example of such a consensus, as is the supposition that the Synoptic Gospels are genetically related to one another in some fashion.
Majority: more than 50% of scholars in the field would affirm a given proposition. That Mark's Gospel was the first written and was used by both Matthew and Luke no doubt falls into this category.
Minority: less than 50% of scholars would affirm a given proposition. That Matthew and Luke also used a second text, designated Q, probably now falls into this category (cf. the recent poll on The Historical Jesus Blog), as does the leading contender, that Luke used Matthew's Gospel and both used Mark's.
Dominant: more scholars would affirm this proposition than any mutually exclusive proposition. By the above definition this would be the case with any majority opinion, such that when I use the word "majority" I necessarily imply "dominant." This category becomes important when considering positions wherein there is no majority but rather only minority positions. The poll to which I referred above suggested that 45% of scholars still hold to Two-Document Hypothesis, or Markan Priority with Q. Let's suggest that of the 55% who reported that they did not 35% hold to the leading contender, Markan Priority without Q, and the other 20% to a variety of other solutions to the Synoptic Problem. We would then say that whilst Q is the dominant view, but not a majority one.
Marginal: a proposition affirmed by a handful of scholars, but which is nonetheless within the realm of respectable scholarship. An example from the study of the Synoptic Problem might be the Augustinian Hypothesis. It has been advocated by a number of scholars who are certainly not cranks, but at any given time the number of proponents probably barely breaks 1% of scholars, if even that many.
Idiosyncratic but respectable: a proposition affirmed by just one, or at most a statistically negligible number of scholars, yet which is sufficiently warranted by the data that it cannot be simply dismissed as quackery. An example might be the arguments in J.A.T. Robinson's Redating the New Testament. For those unfamiliar with his work, Robinson (by no means a conservative) argued that the entirety of the New Testament dates to before 70 C.E. Few have followed him on this. Yet Robinson advances sufficiently robust argument that one who disagrees must bring equally robust counter-arguments.
Quackery: a proposition affirmed by no or at most a statistically negligible number of scholars, and which is so inadequately warranted by the data that it can be dismissed. Jesus's non-existence solidly falls into this category, as does creationism in biology. This has to do ultimately with the robusticity of the argumentation. Whereas idiosyncratic but respectable propositions are supported by robust arguments that fail to persuade many qualified experts, quackery is supported by utterly non-robust arguments. As such the one critiquing quackery need only bring non-robust counter-arguments to bear. Put more colloquially, the idiosyncratic but respectable position requires the critic to bring her or his A-game, whereas the same critic can bring the D-game and still prevail over quackery.
The above are just heuristics, of course, and can be played with as necessary. I simply put them out there for anyone who might find such things helpful.