I am sympathetic to Avner de Shalit’s position that a political philosophy should incorporate public values, but I see their role differently. Philosophers of science standardly distinguish between values being introduced in the context of discovery (inputs into the investigation or arguments) and in the context of justification (acceptance or rejection of substantive claims in light of the arguments or investigation). I argue that de Shalit is wrong to put the public values in the context of discovery; with respect to normative theories (such as political theories), the values should be introduced in the context of justification.