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The pluralistic approach seeks to integrate the explanation of both cognitive development and differentiation within the same theoretical framework. It relies on the fact that a given function can usually be performed by a plurality of processes dealing with different kinds of information. This form of redundancy is assumed to be at the origin of two kinds of relationships between such co-functional processes. On the one hand, relationships of mutual support, which are a source of self-organization and thus of development. On the other hand, relationships of vicariance or substitution, which allow for differences in trajectories over the course of this developmental process. These assumptions are tested by examining available data on number construction in children.