His example concerns the planet Venus which was known as "the evening star" and as "the morning star" before it was realised that both were Venus. Frege argues: "the evening star" = "the morning star" does not have the same sense as "the evening star" = "the evening star" so "the evening star" does not have the same sense as "the morning star". However "the evening star" and "the morning star" refer to the same object so the reference of "the evening star" is distinct from its sense.
Halimbawa ng kanyang pag-aalala ng mga planeta Venus na kung saan ay kilala bilang "ang gabi ng bituin" at bilang "ang umaga bituin" bago ito ay realised na pareho ay Venus. Frege argues: "ang gabi ng bituin" = "ang umaga bituin" ay hindi magkakaroon ng parehong kahulugan bilang "ang gabi ng bituin" = "ang gabi ng bituin" kaya "ang gabi ng bituin" ay hindi magkakaroon ng parehong kahulugan bilang "ang umaga bituin" . Subalit "ang gabi ng bituin" at "sa umaga bituin" sumangguni sa parehong bagay kaya ang reference ng "ang gabi ng bituin" ay naiiba mula sa kahulugan nito.