This paper offers a critique of the idea of 'uncertainty' in the sociology of medicine, particularly in the context of studies of medical education. The work of Renée Fox is used as the main example of the work against which this criticism is levelled. It is argued that the idea of 'training for uncertainty' has been over-emphasized in previous literature. The notion of 'training for certainty' is proposed as a corrective. Finally, however, it is argued that an adequate phenomenology of medical knowledge, education and practice must recognize 'certainty' and 'uncertainty' as two different 'attitudes', which may co-exist simultaneously, reflecting different practical and theoretical interests.