This is a reductive theory of assessment. It is the theory that the assessment of a big thing can be reduced to the assessment of a set of (necessary and sufficient) little things. It is a standards-based theory of assessment. It suggests that we can measure accomplishment by testing for accomplishment of a predefined set of learning objectives.Left to its own devices, though, an open system of assessment is more likely to become non-reductive and non-standards based. Even if we consider the mastery of a subject or field of study to consist of the accomplishment of smaller components, there will be no widespread agreement on what those components are, much less how to measure them or how to test for them.Consequently, instead of very specific forms of evaluation, intended to measure particular competences, a wide variety of assessment methods will be devised. Assessment in such an environment might not even be subject-related. We won't think of, say, a person who has mastered 'physics'. Rather, we might say that they 'know how to use a scanning electron microscope' or 'developed a foundational idea'.