introduction of this approach is to list and analyze the “Jewish” and “Christian” com-
ponents of a particular text or a community, paying special attention to
the question of how its conceptions and practices create, maintain and
cross boundaries between insiders and outsiders.
Thus, a reader who wishes to find a list of necessary and sufficient
traits that would constitute the category of Jewish Christianity will be
disappointed when reading the following pages. No such definition will
be provided. Instead, the basic tenet of the approach is the same as
Jonathan Z. Smith’s “self-consciouslypolytheticmode of classification”
which Matt Jackson-McCabe suggests as a good starting point for the
study of Jewish Christianity (or Christian Judaism). Jackson-McCabe,
however, only presents the general idea of polythetic classification but
does not proceed to discuss the specific “array of traits” that would
constitute the basis of classification.^22 In this respect, the analysis of
indicators goes further. The analysis of indicators is also compatible with
the principles of classification that Daniel Boyarin has brought from
linguistic and cultural studies. These approaches imagine members of
classes as points on a continuum, not as defined through one single
definitive trait.^23
In my view, both Smith and Boyarin have correctly noticed that the
classic Aristotelian idea about classification on the basis of sufficient and
necessary traits is problematic for historians whose data seldom meet the
criteria of pure categories. The idea about categorization through fixed
definitive traits is also incompatible with the way the human brain works.
Therefore, it fails to capture social categorizations from the emic point of
view. In the human mind, categories are formed through exemplars and
prototypes, for which there are separate but parallel running cognitive
systems in the brain. Our brains continuously abstract prototypes from
the available exemplars.^24 This results in flexibility and continuously
(^22) Cf. Jackson-McCabe , –.
(^23) Boyarin , –, –.
(^24) Ground-breaking experiments in this area were conducted by Eleanor Rosch
(Rosch ). Social psychologists and cognitive scientists have disputed the role of pro-
totypes and their relation to exemplars in (social) categorizations. Some have argued for
prototypes as picture-like images of ideal category members (for instance, Brewer )
but self-categorization theorists like Turner and his colleagues (Oakes, et al. , )
have emphasized (drawing on Medin ) the dynamic character of prototypes as con-
textual variables. They also prefer to speak about prototypicality instead of fixed proto-
types. For a more detailed discussion, see Luomanen b, –, –, esp. –
.