Medical practice is always embedded in time and space, whatever its scientific and technical progress could claim as universal truths. The postulate of sincerity is one those contextual elements but it has become so pervasive that a gloss of evidence surrounds it. This situation is at risk of loosing its depth, as much as its limits. By bringing closer together sincerity with more usual notions (transparency, confidence, uncertainty), one could get more insight into these matters of concern in medical practice.