Evidentiary presumptions in law act as shortcuts to rigorous proof. By means of an evidentiary presumption, a difficult-to-prove critical fact may be established by proving some other more easily provable subsidiary fact from which the critical fact may be presumed. This accounts for the popularity of these presumptions with trial lawyers. But the puzzling question has always been, “What effect on the normal processes of trial, does a legal presumption have, especially when there is other evidence pro and con on the presumed fact?” This article aims to shed light on these problems, and to examine the arsenal of tools available to help solve them or at least to help think about solving them. But before we do, we must explore another set of widely misunderstood legal concepts that are key to the inquiry. I am talking about “burdens of proof.” Evidentiary presumptions are exclusively concerned with altering burdens of proof in one way or another. Hence we begin by examining how burdens operate in cases where no presumption is invoked; and then later we will demonstrate how evidentiary presumptions can change the picture.