  Fred Dretske [1988] gave a famous example in this connection. When the soprano's singing of the aria shatters the glass, it will have been facts about the acoustic properties of the singing that were relevant to the breaking. The breaking does not depend upon the fact that she was singing lyrics and that those lyrics expressed such-and-such a content. We therefore expect that it will be the acoustic properties, and not the ‘content’ properties that figure in the pertinent explanatory laws. In the case of action, by contrast, we believe that the contents of the agent's attitudes are causally relevant to behavior. The contents of the agent's desires and beliefs not only help justify the action that is performed but, according to causalists at least, they play a causal role in determining the actions the agent was motivated to attempt. It has been difficult to see how Davidson, rejecting laws of mental content as he does, is in any position to accommodate the intuitive counterfactual dependence of action on the content of the agent's motivating reasons.  His theory seems to offer no explication whatsoever of the fundamental role of mental content in reason explanations. Nevertheless, it should be admitted that no one really has a very good theory of how mental content plays its role. An enormous amount of research has been conducted to explicate what it is for propositional attitudes, realized as states of the nervous system, to express propositional contents at all. Without some better consensus on this enormous topic, we are not likely to get far on the question of mental causation, and solid progress on the attribution of content may still leave it murky how the contents of attitudes can be among the causal factors that produce behavior.