If I am not wrong, the old Fregean distinction between sense and reference can be read in terms of a distinction between intension and extension: The star of the night and the star of the morning are descriptions that share the same extension in the actual world but differ in "sinn", in the sense that they do not pick out the same items in alternative possible worlds.
Yet, as Frege underlines, Phosphorus and Hesperus share the same reference but not the same sense. And, under a rigid designator theory of names, thay also share the same reference in every possible world. But then we must admit that it is not correct to identify intensions with "Sinn". If this is not the right way to capture that concept, how should we analyze the notion of fregean sense? Artwork