We reply to the response by P Calvo, V Raja, and M Segundo-Ortin to our article titled "Plant 'intelligence' and the misuse of historical sources as evidence." Their response draws on the authority of psychologist Edward C. Tolman in support of their suggestion that the study of plant intelligence requires an interdisciplinary approach, including cognitive science and other disciplines. We argue that there is no justification for using Tolman as an authority in support of the study of plant intelligence. For Tolman, psychology was confined to the study of organisms with brains, and therefore his comment, when taken in context, has no bearing on the subject of plant intelligence. Calvo et al.'s use of this quotation is a further example of the misuse of a historical authority to support their claim that disciplines such as cognitive science can be applied to the study of those plant behaviors that they consider to be "intelligent."