The array of different philosophical positions underlying contemporary views on competence, assessment strategies and justification have led to advances in assessment science. Challenges may arise when these philosophical positions are not considered in assessment design. These can include (a) a logical incompatibility leading to varied or difficult interpretations of assessment results, (b) an "anything goes" approach, and (c) uncertainty regarding when and in what context various philosophical positions are appropriate. We propose a compatibility principle that recognizes that different philosophical positions commit assessors/assessment researchers to particular ideas, assumptions and commitments, and applies the logic of philosophically-informed, assessment-based inquiry. Assessment is optimized when its underlying philosophical position produces congruent, aligned and coherent views on constructs, assessment strategies, justification and their interpretations. As a way forward we argue that (a) there can and should be variability in the philosophical positions used in assessment, and these should be clearly articulated to promote understanding of assumptions and make sense of justifications; (b) we focus on developing the merits, boundaries and relationships within and/or between philosophical positions in assessment; (c) we examine a core set of principles related to the role and relevance of philosophical positions; (d) we elaborate strategies and criteria to delineate compatible from incompatible; and (f) we articulate a need to broaden knowledge/competencies related to these issues. The broadened use of philosophical positions in assessment in the health professions affect the "state of play" and can undermine assessment programs. This may be overcome with attention to the alignment between underlying assumptions/commitments.