  There is relatively little mystery about the generation of instrumental and realizer desires. These desires are generated by (conscious or unconscious) reasoning processes, in which one reasons one's way to the conclusion that if only it were the case that p that would make it more likely that q or would be a realization of q. If it so happens that one already intrinsically desires that q, then this reasoning process will automatically and unconsciously generate an instrumental or realizer desire that p, at least in rational beings. (The strength of the new desire, in a rational individual, and all else being equal, increases with the strength of the intrinsic desire that q and the apparent usefulness of bringing it about that p toward bringing it about that q.) Or at least, this picture is a relatively uncontroversial one among philosophers who treat instrumental and realizer desires as components in a causal network that might be investigated by science. Philosophers who approach the mind as a field for interpretation are more likely to hold a non-mechanistic version of this story according to which a person should be interpreted as instrumentally or realizationally desiring p when we already interpret her as intrinsically desiring q and we already interpret her as believing that p would make q more likely.