Table 3 The “6Qs” of a method for appraising the quality of normative literature

What (Element of evaluation, type of normative information)

 • Individual pieces of normative information (individual conclusion, individual argument, individual concept etc.)

 • Whole line of argument (may be identical to part or the whole of the text)

 • Part of the text (paragraph, chapter)

 • Complete text (article, book chapter)

Which (Type of text)

 • Normative ethical text (philosophical)

 • Empirical text

 • Guideline text

 • Jurisprudential/legal text

Where (Methodological procedure/step)

 • As part of the criteria for including or excluding a text (selection)

 • Separate appraisal following the inclusion of the text

 • Appraising the units of analysis (analysis)

 • Appraising the findings (synthesis)

How (Criteria, method)

 • Explicit decision not to carry out a quality appraisal

 • Reporting criteria

 • (Procedural) quality assurance criteria (peer-review process etc.)

 • Content-related quality criteria (e.g. appraisal of individual arguments)

Whereby (Process)

 • Individual researcher

 • Individual researcher reviewed by other researcher

 • Several researchers in a consensus-driven process

 • Several researchers with a comparison of their ratings

Who (Disciplinary/methodological background)

 • Primarily philosophical background

 • Background primarily in the type of normative literature (e.g. law in legal literature)

 • Background primarily in systematic review methodology

 • No specific background (method needs to/can be learned)