Changes

|History=The original definition of the term was proposed by Barseghyan in 2015. It defined ''theory'' as any set of propositions that attempt to describe something.[[CiteRef::Barseghyan (2015)]] As such, this definition excluded normative propositions. It was eventually replaced by the definition suggested by Sebastien in 2016.

|Current View=Currently, ''theory'' is defined as a set of propositions that attempt to describe or prescribe something. Theories can be descriptive (e.g. natural, social, and formal science) or normative (e.g. methodology, ethics, and axiology)[[CiteRef::Sebastien (2016)]]. They may be empirical or formal. They may have different levels of complexity and elaboration; they may consist of thousands of interconnected propositions or, in an extreme, of one single proposition. Examples include Einstein's theory of general relativity, the standard model in particle physics, or the neo-Darwinian theory of evolution [[CiteRef::Barseghyan (2015)|p. 3]].

For the purposes of the theory of scientific change (TSC), a propositional view of theories is adopted. This is because only propositions can have a truth value or be truth-like, and the acceptance and rejection of theories is a core concern of the TSC. While models may play a role in scientific practice, no part of a model may be accepted or rejected unless it can be stated propositionally. If something is not expressible propositionally, at least in principle, it cannot have a truth value, and thus cannot be accepted or unaccepted as the best view of anything [[CiteRef::Barseghyan (2015)| p. 4]].

[[File:Theory_Sebastien_2016_Definition.png|center|390px]]

|Related Topics=Method, Scientific Mosaic

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