The degree of insight into the nature of mental illness that neuroscience can offer depends on the nature of mental illness itself: on whether it is an objective, internal matter or evaluative and socially constituted. But there has been long-standing disagreement about this. To shed light on the debate, I draw on, and refine, Zachar and Kendler’s proposed framework for debating psychiatric taxonomy. I argue that a radical externalist account of mental illness (constitutive evaluativist externalism) threatens the role of neuroscience. But, further, the disagreement between such an evaluativist position and its objectivist opposition may concern not only the nature Professore di Filosofia e Salute Mentale. University of Central Lancashire, Regno Unito. of mental illness but also the terms of the debate. The evaluativist can argue that the disagreement itself is not a factual, but rather an evaluative, matter.
Keywords: Facts, values, Szasz, Zachar, Kendler, taxonomy, neuroscience.