be one that the subject herself can give. The justification provides an argument for the truth of the claim that is known, an argument that the subject can frame. According to epistemic internalism, justification for knowledge claims must be available to those who frame them. This contrasts with epistemic externalism which allows that features that may be beyond the ken of subjects may contribute to their epistemic standing. They may have knowledge, for example, because they have formed their beliefs using reliable processes although this fact (that their processes are reliable) is not known to, or believed by, them.
Internalism is, however, both intuitively appealing and has also been explicitly supported in the history of philosophical discussions of knowledge. In his investigation of knowledge in the Meditations, Descartes assumes that it should be grounded in what could be known with certainty by an individual reviewing his or her own beliefs.
Descartes adopts an internalist view of knowledge which is implicit in his method of attempting to rebuild knowledge of the empirical world in the face of his own sceptical doubts. The method is to start with introspection to deliver self-knowledge which is immune to doubt and then to work back and outwards to knowledge of the empirical world through a series of justifications that he himself can underwrite. This starting point is manifest in passages such as:
I will now close my eyes, I will stop my ears, I will turn away my senses from their objects, I will even efface from my consciousness all the images of corporeal things; or at least, because this can hardly be accomplished, I will consider them as empty and false; and thus, holding converse only with myself, and closely examining my nature, I will endeavour to obtain by degrees a more intimate and familiar knowledge of myself. I am a thinking (conscious) thing, that is, a being who doubts, affirms, denies, knows a few objects, and is ignorant of many,-- [who loves, hates], wills, refuses, who imagines likewise, and perceives; for, as I before remarked, although the things which I perceive or imagine are perhaps Nothing at all apart from me [and in themselves], I am nevertheless assured that those modes of consciousness which I call perceptions and imaginations, in as far only as they are modes of consciousness, exist in me. [Descartes **: **]
But although internalism can seem natural, and receives strong support from Descartes portrayal of the project of grounding knowledge against error, it fails to fit a widespread form of knowledge and one which is particularly important for psychiatry: testimony.
Diagnosis, testimony and internalism
This section will argue that individualism or internalism does not fit with an important aspect of psychiatric diagnosis. Because psychiatric diagnosis depends on testimony and because testimony cannot be understood in internalist terms, an important aspect, at least, of diagnosis does not fit this epistemological perspective. The final section will draw some practical consequences for further empirical study.
Diagnosis depends on testimony. Following established use in philosophy, by ‘testimony’ we mean any form of transmission of knowledge through the reports of others. It thus contrasts with perception, reasoning, whether inductive or deductive, and memory. Testimony plays a role in psychiatry because symptoms are elicited from patients through informal questioning and conversation or more formal structured or semi-structured interviews. In these contexts, clinicians acquire knowledge of their patients’ mental states in ways which go beyond their (the clinicians’) own direct observations.
This is not to advocate a view of the mind as closed off from the public world and subject only to hypothesis by others. There is logical space between such a view, often called ‘Cartesianism’, and its polar opposite, behaviourism, according to which mental states lies literally open to view by being logical constructs from behaviour, describable in non-mental terms [McDowell 1982]. Between these extremities lies the more plausible view that whilst the mental states of others are not literally open to view, their expressions are.