Ever since the Council of Trent defined that ‘in the Mass is offered a true and proper Sacrifice’ (Cone. Trid. Sess. XXII, De Sacrificio Missae. Can. i), theological speculation in the schools has been rife evolving multifarious theories as to how the Mass is a Sacrifice, or what it is that formally determines the sacrificial character of the Mass. Various views have been advanced with which famous names of the Society of Jesus are identified, as, for instance, Vasquez, de Lugo, Perrone, Franzelin, Schouppe, Pesch and Billot. These theologians unanimously agree that the immolation of the Victim in the Sacred Passion is itself the complete Oblation or Sacrifice of Redemption, and that this Immolation was an Act of Sacrificial Oblation distinct from, and subsequent to the Last Supper. Not one of these theologians even implies that Immolation is not itself the complete act of Sacrificial Oblation. For example, Cardinal Billot, whom justly P&re de la Taille calls a Prince of Theologians, teaches that Immolation is the Sacrificial Oblation of a bloody Sacrifice whether the term be applied to the Mosaic Sacrifices or to the Sacred Passion (cf. Billot, De Sacrific. Miss. Thesis liv, § 2). In the elaboration of their views—although conceivably we may not entirely agree with any one of them—it is notable that on the subject of the Redemptive Sacrifice they keep strictly within the limits traced by theological Tradition and the Council of Trent.