The study aims to offer an overview of the chief problems in the theory of the moral act, in the light both of the doctrinal determinations furnished by the encyclical "Veritatis Splendor", and of the discussion and investigation of these in the philosophical and theological literature. The author holds that the origin of the doctrinal difficulties in proportionalism and consequentialism lies in their way of conceiving the nature and constitution of the moral object. Concerning this specific problem the encyclical "Veritatis Splendor" offers important methodological indications.