 Jonathan Dancy (Dancy 1993, 2004) has developed and defended an anti-Humean conception of practical reasoning, according to which it is the facts themselves, and not our desires, aversions, or other attitudes towards those facts, that constitute reasons for acting. These facts consist of particulars’ having properties, and those properties provide in each such case some reason for acting--as, for example, someone’s need can provide a reason for meeting that need. However, each general property can provide a reason only defeasibly: not only can a reason be overwhelmed by contrary considerations, but a property’s valence for action can be completely neutralized or even reversed by further considerations. For example, even if giving pleasure is in general a reason in favor of acting in a certain way, the fact that some action would give pleasure to those pleased by the suffering of others is a reason  against and not for so acting. Dancy has introduced (in Dancy 2004) the concepts of intensifiers and attenuators, applying to facts that strengthen or weaken the force of reasons. In the extreme case, a fact can disable a reason altogether, corresponding to what Joseph Raz had described as an exclusionary reason (Raz 1975), and to John Pollock’s idea of an  undercutting defeater.