 The biggest challenge to characterizing abstracta as causally inefficacious entities is that causality itself is a notoriously problematic and difficult to define idea. It is undoubtedly one of the most controversial notions in the history of thought, with all kinds of views having been put forward on the matter. Thus, causally efficacious inherits any unclarity that attaches to causality. So, if we are to move the discussion forward, we need to take the notion of causation—understood as a relation among events—as sufficiently clear, even though in fact it is not. Having acknowledged this no doubt naïve assumption, several difficulties arise for the suggestion that abstract objects are precisely the causally inefficacious objects.