Manfred Pienemann offers an interesting, fair-minded, and systematic account of the role of processability constraints in explaining language development. Thus he opens up a wide field of research in the area of the interaction of grammatical knowledge and processing constraints, and Pienemann should be applauded for this kick-off. In my view, this field should be explored in a non-partisan manner. Rather than pushing either grammar or processing at the expense of the other, we should be looking at the division of labour between different mental capacities, and at potential sites of overlap, conflict, and convergence. L2 development is crucial in this research, because it may show how much can be accomplished with non-grammatical processing. I will limit myself here to a number of disjointed remarks on some directions for research.