According the German logician Gottlob Frege (1848–1925), linguistic units have two dimensions of meaning, reference (Bedeutung) and sense (Sinn). The referent of a name is an object; the referent of a predicate is a concept (a function from objects to truth values); the referent of a (declarative) sentence is truth value (true or false). The sense of a unit is the way by which the referent is grasped. The sense of a sentence is a thought (or proposition). Words with different senses can refer to the same object. Thus ‘the Morning Star’ and ‘the Evening Star’ have different senses, but both denote the planet Venus.