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Presumptions have an important role in antitrust jurisprudence. This article suggests that a careful formulation of the relevant presumptions and associated evidentiary rebuttal burdens can provide the “enquiry meet for the case” across a large array of narrow categories of conduct confronted in antitrust to create a type of “meta” rule of reason. The article begins this project by using decision theory to analyze the types and properties of antitrust presumptions and evidentiary rebuttal burdens and the relationship between them. Depending on the category of conduct and market structure conditions, antitrust presumptions lie along a continuum from conclusive (irrebuttable) anticompetitive, to rebuttable anticompetitive, to competitively neutral, and on to rebuttable procompetitive and conclusive (irrebuttable) procompetitive presumptions. A key source of these presumptions is the likely competitive effects inferred from market conditions. Other sources are policy-based -- deterrence policy concerns and overarching policies involving the goals and premises of antitrust jurisprudence. Rebuttal evidence can either undermine the facts on which the presumptions are based or can provide other evidence to offset the competitive effects likely implied by the presumption. The evidentiary burden to rebut a presumption depends on the strength of the presumption and the availability and reliability of further case-specific evidence. These twin determinants can be combined and understood through the lens of Bayesian decision theory to explain how “the quality of proof required should vary with the circumstances.” The stronger the presumption and less reliable the case-specific evidence in signaling whether the conduct is anticompetitive versus procompetitive, the more difficult it will be for the disfavored party to satisfy the evidentiary burden to rebut the presumption. The evidentiary rebuttal burden generally is a burden of production, but also can involve the burden of persuasion, as with the original Philadelphia National Bank structural presumption, or typical procompetitive presumptions. If a presumption is rebutted with sufficient offsetting evidence to avoid an initial judgment, the presumption generally continues to carry some weakened weight in the post-rebuttal phase of the decision process. That is, a thumb remains on the scale. However, if the presumption is undermined, it is discredited and it carries no weight in the post-rebuttal decision process. The article uses this methodology to analyze various antitrust presumptions. It also analyzes the, burden-shifting rule of reason and suggests that the elements should not be rigidly sequenced in the decision process. The article also begins the project of reviewing, revising and refining existing antitrust presumptions with proposed revisions and refinements in a number of areas. The article invites other commentators to join the project by criticizing these proposals and suggesting others. These presumptions then could be applied by appellate courts and relied upon by lower court, litigants and business planners.