 It is also widely held that in addition to having such properties as reference, truth-conditions and truth – so-called extensional properties – expressions of natural languages also have intensional properties, in virtue of expressing properties or propositions – i.e., in virtue of having meanings or senses, where two expressions may have the same reference, truth-conditions or truth value, yet express different properties or propositions (Frege 1892/1997). If the semantic properties of natural-language expressions are inherited from the thoughts and concepts they express (or vice versa, or both), then an analogous distinction may be appropriate for mental representations.