In the introduction to his book On Desire, William Irvine writes, "My goal in investigating desire was to turn it inside out -- to understand how and why desires arise, how they affect our lives, and what we can do to master them." This goal is (or these goals are) certainly worthy, and Irvine does deliver in many respects; however, he begins with too many conceptual confusions to make the work entirely satisfying.
Early on, Irvine asserts that "we are awash in desire at virtually every waking moment." Some of these are "terminal" and others are "instrumental." If this is true, then Irvine's definition of desire is so weak as to be nearly useless. Later, he backs off of this claim to some extent, but it nonetheless haunts his work to the end. What is missing here is any serious consideration of behavior that is habitual or proceeding from efficient causes. This is particularly true in his treatment of instrumental desires. Desiring a meal (a terminal desire) an agent will experience a sequence of instrumental desires, e.g., desiring one's car keys, desiring to open the car door, desiring drive to the restaurant, to find a parking place, to get a table, etc. While one might categorize these as desires, one might also treat them simple as actions that unfold from a prior decision to go to the restaurant. The ad absurdum analysis would posit a separate desire for each foot step along the way. Irvine also fails to examine the distinction between actions and non-actions. Do I desire to continue sitting in my chair or am I simply still sitting in it? The answer is probably different in different circumstances, e.g., sitting while the "yeas" are counted in a parliamentary vote vs. sitting in the waiting room of a bus terminal.
Irvine distinguishes between desires that are born of emotions and those born of the intellect. The former is particularly effective in establishing terminal desires, while the latter is effective in establishing instrumental desires, but the correlation is not perfect. Acording to Irvine, the intellect can create a terminal desire to "click one's tongue." Such terminal desires are, of course, rare and weak in comparison to emotional desires. According to Irvine, his treatment of desires follows from most of what Hume says about the sources of our motivations. I suspect this is incorrect. Hume famously wrote that reason is the slave to passion. Reason is able to assess truth and falsity, but action is generated by passion.
Setting aside whether or not Irvine is correct about Hume, his treatment of the intellect and its power to act deserves a much fuller explanation. In some instances, "intellect" amounts to the ability to comprehend language, but it is hard to separate such a fundamental ability from other fundamental abilities, e.g., simple sense perception. Is understanding that certain sounds have a meaning much different than understanding that certain other sense perceptions have a significance? If not, then is it an excercise of the intellect to understand that the colors and shapes appearing before me are a tree? And to what extent are simple sense perceptions components of our emotional states? If perceptions are implicated in emotions, then it would appear that the boundaries between the intellect and emotion are blurred and they may not bear the distinction that Irvine purports.
Irvine would have done better to avoid the emotion-intellect distinction and examine instead the passion-reason distinction that is made by Kant. It is noteworthy that he makes no mention of Kant at all. If he had, his treatment of desires and mental faculties likely would be more insightful and engaging. As it is, his treatment relies too heavily on a naive hedonism, dressed up in a not terribly useful discussion of what he calls a "biological incentive system." Irvine points out that we are born with and presumably naturally develop specific likes and dislikes that have served our survival over evolutionary time. This seems true enough, but he offers no persuasive account as to how we might overturn or even resist these natural tendencies. Having such an account is critical to the final chapters of his work which seek to explain how people have learned to "master" their emotions.
Irvine's last six chapters (out of thirteen) explore "dealing with our desires." He examines the advice and practices of Buddhists, mainstream Christians, the Amish, Hutterites, and Shakers; Stoics, Epicureans, and Skeptics; as well as people he calls "eccentrics." In each instance, the practices amount to "mastering" our desires, but again, Irvine does not explain the psychological basis upon which this is made possible, beyond noting that our desires do not preclude our freedom. Of course, presenting an account of freedom would expand the work considerably, but it is nonetheless central to the questions he seeks to answer. At very least, a more detailed treatment of the ecology of desires as they fit into the various (sometimes conflicting) long and short-term projects which each of us have probably would be consistent with Irvine's overall approach and would deepen his treatment of the questions at hand.