The task of this paper is to clarify the status and implications of Levinas's insistence on the necessity of subjectivity to the ethical relation. Focusing in particular on the discussion of substitution in Otherwise than Being, it is argued that the description of subjectivity as substitution enables Levinas to articulate the necessity of the subject to the approach of the other in a manner which avoids the transcendental character which such claims to necessity usually embody. This argument proceeds from an initial characterization of substitution within the constellation of themes pursued by Levinas in Otherwise than Being to a detailed examination of the first four sections of the "Substitution" chapter. The essay concludes by noting the unity of the ethical exceeding of the transcendental character of subjectivity with the project which animates Levinas's work from its beginnings: the exceeding of the ontological by the ethical.