 (See the entry on  logic, classical.)  Fregean formalized languages include also classical higher-order languages. (See the entry on  logic, second-order and higher-order.)  The logical expressions in these languages are standardly taken to be the symbols for the truth-functions, the quantifiers, identity and other symbols definable in terms of those (but there are dissenting views on the status of the higher-order quantifiers; see 2.4.3 below).