Requirements for accreditation of medical professionals are increasingly cast in the language of general competencies. Because the language of these competencies is generally shaped by negotiations among stakeholders, however, it has proven difficult to attain consensus on precise definitions. This lack of clarity is amplified when attempting to measure these essentially political constructs in individual learners. The authors of this commentary frame these difficulties within modern views of test validity. The most significant obstacle to valid measurement is not necessarily a lack of useful tools but, rather, a general unwillingness to question whether the competencies themselves represent valid measurement constructs. Although competencies may prove useful in defining an overall social mission for organizations, such competencies should not be mistaken for measurable and distinct attributes that people can demonstrate in the context of their actual work.