1. A supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
    1. A set of principles on which the practice of an activity is based.
    2. An idea used to account for a situation or justify a course of action.

Design Academy Eindhoven has a particular approach to theory in as much as a distinction between theory and practice is barely made in the coursework. Design Academy Eindhoven strives toward a curriculum whereby theory, or the forming of theory, becomes an integral part of the design process.

In scientific research, the word theory refers to a set of propositions that can be used as principles of explanation and the prediction of phenomena. In a less strict sense, the word is used to indicate a particular conception or view of something, as well as a principle underlying a certain practice. At most art academies theory refers to courses that are not practical in nature – courses in which something is not crafted with the hands, but in which the head is put to work to think something through – dissecting the meaning of the word art, the differences between cultures, or basic principles of design, etc.

Theory should not be confused with method. Where theory proposes an explanation, method refers to a way of working (following a certain procedure). So, a method can be used to test a theory. For instance, through rigorous investigation a hypothesis (a proposed explanation) can be tested and a new theory formed.

In the field of design, theory is often associated with reading and writing, as opposed to doing something practical. In design research however, theories can also be developed, challenged and tested by designers engaging in hands-on research and experiments with materials.