  An expression's sense is intended to capture its cognitive value. The above argument is intended to show that  coreferential proper names can present the same object in different ways and it can be a cognitive achievement to come to learn that the object presented in those different ways is one and the same. Reference alone, Frege persuasively argued, cannot capture cognitive value. Capturing the cognitive significance of an expression is a primary role senses played in Frege's system. But they also played several other roles as well: They are the primary bearers of truth values, the indirect references of sentences and hence the objects denoted by that clauses like ‘that Frege denied the existence of singular propositions’, and the objects of propositional attitudes, most importantly. These roles give rise to the following theses concerning the individuation of senses.