The second model is the application of a function to an argument. The result of applying a function to an argument is not (normally) a complex consisting of the function and the argument.It is, rather, the value of the function for that argument. This model of composition is the one Frege ultimately applies in the realm of reference:A concept is a function from objects to truth-values, and the reference of a (non-embedded) sentence is its truth-value; “Frege had a beard” refers to the truth-value that is the result of applying the ‘concept-function’ denotedby the predicate to the object denoted by the subject.