Full Idea
The evening star is the same planet but not the same star as the morning star. For Venus is not a star.
Gist of Idea
The evening star is the same planet but not the same star as the morning star, since it is not a star
Source
David Wiggins (Sameness and Substance Renewed [2001], 2.3)
Book Reference
Wiggins,David: 'Sameness and Substance Renewed' [CUP 2001], p.29
A Reaction
This is a nice objection to the idea that identity is entirely a matter of falling under the same sortal category.