This paper focuses on the evolution of “reasonableness” as a unitary standard of judicial review and the role of tribunal expertise in that process. The modern era begins with Nipawin in 1973, a time when judicial review operated with a crude binary system of standards that allowed for either full curial deference (patent unreasonableness) or no deference (correctness). It ends in 2008 with Dunsmuir and the jettisoning of the highest standard of curial deference, the standard of patent unreasonableness. Correctness is now implicitly understood not as a standard but, as the justified absence of the need to extend deference to a tribunal`s decision. Patent unreasonableness and the middle ground standard of reasonableness have ostensibly been "collapsed" into a single more rational, workable, flexible and sophisticated unitary system based on the multi faceted standard of reasonableness. It is argued that the new “standard of review analysis” expressed in Dunsmuir is simply a comprehensive restatement of all the previously articulated diverse and, typically, non-dispositive factors and exceptions. The hallmarks of this new standard are the recognition that, more often than not in administrative law, there is no one right or best answer and that, a reviewing court will respect and affirm a tribunal’s choice if it is within the range of options provided it is well reasoned. This paper also addresses the primarily academic criticism of the Supreme Court over conceptual problems in distinguishing patent unreasonableness from reasonableness, a dispute fuelled by this court’s continued attempts to justify a standard of review that allowed for a tribunal’s right to be wrong. It is argued that patent unreasonableness had become less of a standard of review and more of a simple expression of judicial censure for egregious fault in decision making; a qualifier to a finding of unreasonableness. Arguably that role may have been preserved even with the collapsing of the two standards into one standard in Dunsmuir. While Dunsmuir should have clarified many of the issues the three-way difference of opinion in the Court demonstrates continuing deep rifts that may portend further uncertainty. Uptake by lower courts indicates otherwise. / Thesis (Master, Law) -- Queen's University, 2009-03-17 14:58:15.299