John Gabbay and Andrée le May, professors emeriti in public health and nursing respectively, have both been engaged for decades in trying to help clinicians use research evidence. Their recent ethnographic work, which aimed to understand why that task often seems such an uphill struggle, led to the theory of ‘mindlines’, which is increasingly popular among those charged with implementing health-service research. Mindlines, which incorporate evidence from many sources, are complex, flexible, internalised guidelines developed over a lifetime. Often collectively shared between colleagues through casual conversation, mindlines are more able than guidelines to respond to the conflicting contextual demands of practice. The talk will consider both the epistemological and practical implications of their theory. Watch out for the potty-putty pinball machine.