Abstract

One of the central aims of Susanne Mantel’s book "Determined by Reasons" (2018) is to reject the idea that normative and motivating reasons can be identical. In her own words, Mantel denies the “Identity Thesis”, according to which “when an agent acts for a normative reason N, there is a motivating reason M of that agent such that M is identical with N” (Mantel 2018, 93). In this comment, I offer a simple argument for the Identity Thesis: (1) When an agent acts for a normative reason N, there is a reason M for which that agent acts such that M is identical with N. (2) A reason for which someone acts is a motivating reason. (3) Therefore, when an agent acts for a normative reason N, there is a motivating reason M of that agent such that M is identical with N. Premise (1) is trivial, and premise (2) is true by a common definition of the term ‘motivating reason’, according to which a motivating reason is just a reason that is acted upon. I call this the operative notion of a motivating reason. Mantel does not address this operative notion, even though it is widely used in the literature, especially among proponents of the Identity Thesis. I argue that Mantel does not succeed in rejecting the Identity Thesis as long as she does not show that the operative notion of a motivating reason is flawed.