What is the general principle regarding entertaining new issues on appeal?

The general principle regarding entertaining new issues on appeal was articulated by Weiler J.A. in Kaiman v. Graham, 2009 ONCA 77 (CanLII), 245 O.A.C. 130, at para. 18: The general rule is that appellate courts will not entertain entirely new issues on appeal. The rationale for the rule is that it is unfair to spring a new argument upon a party at the hearing of an appeal in circumstances in which evidence might have been led at trial if it had been known that the matter would be an issue on appeal… The burden is on the appellant to persuade the appellate court that “all the facts necessary to address the point are before the court as fully as if the issue had been raised at trial”… This burden may be more easily discharged where the issue sought to be raised involves a question of pure law… In the end, however, the decision of whether to grant leave to allow a new argument is a discretionary decision to be guided by the balancing of the interests of justice as they affect all parties… [citations omitted.]