例如，啟明星係長庚星。（雖然各自叫法唔同，但佢哋都係金星嘅名稱）。佢哋必然係同一樣嘢，但呢一種同一性係由後驗得知。
For example, the morning star is the Chang Gung star. (Although they are called differently, they are both the names of Venus). They must be the same thing, but this identity is known a posteriori.