Issues surrounding the role and provision of evidence to inform policy and practice have become topical and problematic. The context of these controversies is discussed, with particular emphasis on systematic approaches to synthesising research evidence. We contrast the ‘positivist’ emphasis with interpretative qualitative synthesis, and suggest that many of the viewpoints have become unnecessarily and unhelpfully polarised. The methods for systematic research syntheses will vary as they depend on the question being asked. The process is transparent, allowing readers to see how conclusions have been reached, and forms the basis of reviews which can be updated to help provide sustainable and relevant evidence.