Abstract
I develop and defend a model of downward causation denoted as downward, structural, substance causation. This model is based on the idea that higher-level, strongly emergent substances can cause something at lower levels by imposing certain structures on lower-level goings-on. After providing a sketch of the model and of its ontological assumptions, I apply it to the analysis of how free mental causes can structure neural goings-on. I defend three theses following from such an analysis, and I test the empirical plausibility of the model. Finally, I anticipate some objections and replies.