 However, this defence of the positive-negative distinction as coinciding with the distinction between exercise- and opportunity-concepts of freedom has been challenged by Eric Nelson (2005). As Nelson points out, most of the theorists that are traditionally located in the positive camp, such as Green or Bosanquet, do not distinguish between freedom as the absence of constraints and freedom as the doing or becoming of certain things. For these theorists, freedom is the absence of any kind of constraint whatsoever on the realization of one’s true self (they adopt a maximally extensive conception of constraints on freedom). The absence of all factors that could prevent the action x is, quite simply, equivalent to the realization of x. In other words, if there really is nothing stopping me from doing x — if I possess all the means to do x, and I have a desire to do x, and no desire, irrational or otherwise, not to do x — then I do x. An equivalent way to characterize the difference between such positive theorists and the so-called negative theorists of freedom lies in the degree of specificity with which they describe x. For those who adopt a narrow conception of constraints, x is described with a low degree of specificity (x could be exemplified by the realization of any of a large array of options); for those who adopt a broad conception of constraints, x is described with a high degree of specificity (x can only be exemplified by the realization of a specific option, or of one of a small group of options).