 To clarify this, consider the example of Hal’s glucose metabolism (Craver &amp; Bechtel 2007: 559–560). Hal is playing tennis, and as he keeps running around and swinging the racket, the cells in Hal’s body start taking in and using more glucose. It seems that the cause of the increase in Hal’s glucose metabolism at the cellular level is Hal playing tennis, which suggests causation from a higher level (the level of the whole organism playing tennis) to a lower level (the cellular level). However, in the framework of Craver and Bechtel described above, what is really going on is just regular same-level causal relationships at the cellular level: Nerve signals to the muscle cells cause a cascade of events that results in increased glucose metabolism. Hal’s tennis playing activity is partly constituted by these cellular mechanisms, and this constitutive relationship is responsible for the illusion of downward causation. As Hal starts to play, there are changes in these mechanisms, but only in virtue of them partly making up the tennis playing activity.