ABSTRACT
Professional practitioners act or decline to act, feel confident or uncertain they have a sound basis for their actions and decisions, draw prescriptions or confess agnosticism, and all in the light (or gloom!) of the best evidence they can reasonably assemble. But what is the status of such evidence? Can professionals safely act on the assumption that it provides a good enough approximation to reality, which will transfer to similar new situations? Or should they remain deeply sceptical of all similar information on the grounds that it is the contingent, relative product of a unique local context, and may also represent the interests and constructions of the powerful?
