  We can think of this first approach as zooming-in on one small portion of the overall network, looking for a unit that has enough stability across histories to allow for an explanation in which there are cause-effect regularities; if the underlying causal structure is too diverse, look for causal units that stably replicate across patients, explain them, and then put these well-understood parts together to explain individuals. Another advantage of this approach is that it promises to treat patients as individuals rather than clumping together into kinds that they only approximately fit.