Discussions of party system change may be unsatisfactory if insufficient attention is given to the defining properties of a system. A number of dimensions have to be considered, but - as with `social cleavages' - there can be disagreement as to whether a truly constitutive element is involved. In addition, it is necessary to distinguish the various degrees of change that are possible, and in this respect a study of the process of change is essential. Party system typologies are of little help, so that an alternative in the form of `working models' can be employed. The emphasis in this approach is on the identification of the `core components' of the particular system against which the degree of change can be assessed. An examination of representative West European party systems reveals that these core components show a strong persistence.
