The natural language sentence

• • Some critics admire only one another.

The sentence is notable for presenting a natural and easily understood sentence that is nonfirstorderizable, that is, for which there is no corresponding sentence in the language of first-order logic using predicates ‘$x$ is a critic’ and ‘$x$ admires $y$’, a fact proven by philosopher David Kaplan (1930– ).

To capture the Geach-Kaplan sentence requires higher-order quantifiers, e.g., it is known to be adequately expressible in logic with plural quantification.