Some will say that in such cases the desire causally explains the waving, but that it is still the brain state that causes it. This thought appeals to the intuition that real causal relations are always constituted by basic physical interactions, by bits of matter bumping into each other. But this intuition is not decisive, and a number of theoretical considerations speak against it.  For instance, the “difference-making” account of causation developed by James Woodward implies that generic properties often eclipse their more specific realizations as causes (Woodward 2005), as does the view that causation is a relatively macroscopic phenomenon whose temporal asymmetry is analogous to the temporal asymmetries of thermodynamics (Loewer 2007, Papineau 2013).