Delusions are deeply evidence-resistant. Patients with delusions are unmoved
by evidence that is in direct conflict with the delusion, often responding to such
evidence by offering obvious, and strange, confabulations. As a consequence,
the standard view is that delusions are not evidence-responsive. This claim has
been used as a key argumentative wedge in debates on the nature of delusions.
Some have taken delusions to be beliefs and argued that this implies that belief
is not constitutively evidence-responsive. Others hold fixed the evidenceresponsiveness
of belief and take this to show that delusions cannot be beliefs.
Against this common assumption, I appeal to a large range of empirical evidence
to argue that delusions are evidence-responsive in the sense that subjects have
the capacity to respond to evidence on their delusion in rationally permissible
ways. The extreme evidence-resistance of delusions is a consequence of powerful
masking factors on these capacities, such as strange perceptual experiences, motivational
factors, and cognitive biases. This view makes room for holding both that
belief is constitutively evidence-responsive and that delusions are beliefs, and it
has important implications for the study and treatment of delusions.