  Many proponents of the instrumental principle would agree that it does not generate reasons for action. The fact that a given means is necessary, relative to one’s given ends, is not a reason to take the means. The instrumental principle functions, rather, as a structural requirement on one’s attitudes (Broome 1999, Broome 2004). Thus, suppose one intends end E, and believes (truly) that E can be achieved only if one intends to do M. It appears that there are two ways in which one could revise one’s attitudes in response to these considerations, compatibly with the instrumental principle: one could form the intention to M, or one could abandon one’s original intention to E. The instrumental principle, considered in itself, is indifferent as between these two possibilities; it should be understood as a wide-scope requirement, governing combinations of attitudes, rather than a source of detachable normative conclusions about what one has reason to do. (Modus ponens represents a similar rational requirement in the domain of theoretical reason, governing combinations of beliefs.)