Still other mechanists, such as Bogen (2005, 2008a) and Machamer (Machamer 2004), embrace an Anscombian, non-reductive view that causation should be understood in terms of productive activities (see also the entry on   G.E.M. Anscombe). Activities are  kinds of causing, such as magnetic attraction and repulsion or hydrogen bonding.  Defenders of activity-based accounts eschew the need to define the concept, relying on science to say what activities are and what features they might have. This view is a kind of causal minimalism (Godfrey-Smith 2010). Whether an activity occurs is not a matter of how frequently it occurs or whether it would occur always or for the most part in the same conditions (Bogen 2005).