If the ability to follow one's nose depends on freedom from presuppositions, wishes, preconceptions and theoretical investment, or, to put it another way, on the ability to pursue hunches or ``build out into the dark'', then the ability to doubt what one knows (or rather what one thinks one knows) would seem to be close to the heart of the matter. Hand in hand with room for doubt and healthy skepticism goes a free imagination ± the ability seriously to consider all possibilities, unfettered by preconceptions. And as initial skepticism is necessary for a free imagination, a free imagination is required for ®rm convictions. I will try to illustrate this point with some clinical examples.