 Mill offers at least three different accounts of the contribution which the psychological science of reasoning makes to the art of reasoning. On the first account, the prescriptive art of reasoning seems prima facie independent of psychological science. In this vein Mill writes, for example, that psychology can only offer ‘the analysis of the mental process which takes place whenever we reason’, whereas the art of reasoning must provide ‘the rules … for conducting the [reasoning] process correctly’ (1843, 4). A second account is based on the idea that any successful prescription for a given type of thought process must be based on a proper and detailed psychological understanding of that process: ‘A right understanding of the mental process itself … is the only basis on which a system of rules, fitted for the direction of the process, can possibly be founded’ (ibid.). And Mill’s third account goes further still: ‘Its [the Science of Logic’s] theoretic grounds are wholly borrowed from Psychology, and include as much of that science as is required to justify the rules of the art’ (1865, 359). On the third account, psychology is essential to the justification of the rules of reasoning. Mill provides no clear indications on how these prima facie conflicting statements can be reconciled. Clearly the third statement will qualifies as psychologistic by everybody’s criteria — though doubts have been raised whether, ‘when this passage is read in its full dialectical context’, it amounts to more than the claim that ‘the logician must formulate rules of inquiry in a manner which will be as helpful as possible to inquirers, and must draw on the psychology of thought to do so’ (Skorupski 1989, 166). But even the first two accounts, interpreted against the backdrop of Mill’s other views, make prescriptive logic dependent upon psychology. Logic cannot begin its task until psychology has provided a descriptive analysis of reasoning processes.