This keynote article proposes a new model of language development based on processing, the sole mechanism of acquisition for the Acquisition by Processing Theory (APT). The language module – adapted from Jackendoff's distinction between integration (building complex structures) and interface (facilitating information transfer at the intersections of the sub-modules) – has phonological, syntactic and conceptual processors that interact with each other, working memory and lexical entries. On the one hand, the application of Jackendoff's model to language learning bridges a gap between syntactic theory and processing. On the other hand, its breadth sometimes brings together strange bedfellows, as, for example, minimalist syntax and APT's ‘clear affinities with connectionism’ (p. 17). In order to explore this hybrid model within a focused area, I will limit my comments to a discussion of features of I(nflection), Case and thematic (theta) roles, highlighting the question of how much syntactic theory APT needs. I will suggest that the model could profit from a greater exploitation of morphological input and its role in parameter setting.