In the sciences, a scientific theory (also called an empirical theory) comprises a collection of concepts, including abstractions of observable phenomena expressed as quantifiable properties, together with rules (called scientific laws) that express relationships between observations of such concepts. A scientific theory is constructed to conform to available empirical data about such observations, and is put forth as a principle or body of principles for explaining a class of phenomena.[1]
A scientific theory is a type of deductive theory, in that its content (i.e. empirical data) could be expressed within some formal system of logic whose elementary rules (i.e. scientific laws) are taken as axioms. In a deductive theory, any sentence which is a logical consequence of one or more of the axioms is also a sentence of that theory.[2]
In the humanities, one finds theories whose subject matter does not (only) concern empirical data, but rather ideas. Such theories are in the realm of philosophical theories as contrasted with scientific theories. A philosophical theory is not necessarily scientifically testable through experiment.