This paper discusses Frege’s views on how Fregean senses, Sinne, should be individuated, and what chances we have of arriving at knowledge about them. There is a conflict in Frege’s views. First he introduces a criterion of sameness of sense which requires that speakers are authoritative concerning senses, then holds that there are cases where no one knows the sense of an expression. If no speaker is authoritative concerning sense, then the original criterion for sameness of sense cannot be upheld. But Frege repeatedly emphasized the need for criteria of identity. This paper discusses the conflict between the different things Frege wants to say about sense, and points to possible ways out of the problems.