What is a common issue in a class action?

A common issue is an issue of law or fact shared by the members of the class that will move the litigation forward. In Campbell v. Flexwatt, supra, Cumming J.A. said the following at paras. 51-54: The Class Proceedings Act requires that the claims of the class members raise common issues which, for reasons of fairness and efficiency, ought to be determined within one proceeding. Common issues can be issues of fact or law and do not have to be identical for every member of the class. Section 1 of the Class Proceedings Act defines common issues as: (a) common but not necessarily identical issues of fact; or (b) common but not necessarily identical issues of law that arise from common but not necessarily identical facts. This question of commonality of issues lies at the heart of a class proceeding, for the intent of a class proceeding is to allow liability issues to be determined for the entire class based on a determination of liability of the defendants to the proposed representative plaintiffs. When examining the existence of common issues it is important to understand that the common issues do not have to be issues which are determinative of liability; they need only be issues of fact or law that move the litigation forward. The resolution of a common issue does not have to be, in and of itself, sufficient to support relief. To require every common issue to be determinative of liability for every plaintiff and every defendant would make class proceedings with more than one defendant virtually impossible. Where there is a large number of individual issues arising out of the common issues to be addressed, courts have restricted the common questions in order to maintain the desirability of the class proceeding as the preferable procedure.