What is the difference between a mortgage and an agreement of sale?

That there is a fundamental difference between the relative positions of mortgagee and mortgagor on the one hand, and vendor and purchaser on the other, is well illustrated by the observations of Anglin J. in Davidson v. Sharpe, 1920 CanLII 83 (SCC), 60 S.C.R. 72, [1920] 1 W.W.R. 888 at 894-7, 52 D.L.R. 186. He says that there is an essential difference between judgment for foreclosure in a mortgage action and an order or judgment for cancellation of an agreement of sale due to the difference between a mortgage and such an agreement. The foreclosure judgment in the mortgage action is merely a means of enforcing the mortgage contract which it deals with as specified, whereas a judgment for recission or cancellation of a contract between vendor and purchaser is a judgment, not for enforcement but for extinguishment of a contract. He points out that the anomalies introduced by courts of equity in regard to the relations between mortgagor and mortgagee do not exist in regard to vendor and purchaser and that the judgment or order declaring that on the happening of a certain event an agreement of sale shall be cancelled and at an end means precisely what it says and not merely that the plaintiff shall thereupon be entitled to have it cancelled and put an end to. He explains that after such an order a purchaser had no further right to the land and the court has no jurisdiction to restore him to his former position.